I started pretty much where you are. I ended up with a 393, trick flow heads and pistons, etc. My 700R4 has pretty much the same road ratios as you ZF. Its real easy to look at a crankshaft that needs machine work and say for $100 more I can have a 393, or look at a set of E7 heads that need machine work and realize that a good set of assembled aluminum heads is just a little more money. Thats how I got here and I would go back but if my FTE was low milage and ran fine when I got it I would NOT have gone this route and would have been happy with it too.
All these engine mods add up and can be used for wheels, tires, lockers, etc.
What I am going to say here will get a lot of people telling me I am crazy.
First, if budget is a concern and if your FTE runs good just leave it alone. It is way more torque and HP than anything Ford ever put in a bronco. Save your money for things other things. You will likely be happy with the FTE and E7 heads.
If you do make modifications to the engine always keep in mind what you are driving. A bronco is a brick with straight axle 1960s technology suspension and even if you upgrade to front dics you are still talking 1970s technology brakes. I start to get white knuckles at 90 MPH and I am comfortable cruising at 80 MPH. The High lift long duration cams the Mustang crowd will tell you that you need are a total waste in a Bronco. The cam you have in the FTE isn't really a bad street off road cam, and is about all the duration you need. But you can get more lift. If you buy a cam buy the highest lift you can with a relatively short duration like the FTEs cam. They will be listed in a 5.0 to make peak power about 5000 RPM. If fact if you choose to replace intakes, headers, etc everything should be selected to make peak horsepower at 5000 RPM in a 5.0. If everything you select is max at 5000 your peak should be higher than 4500 in a 351W. But the reality is that the larger displacement will shift that peak upwards. My 393 HP peaked at 5500 RPM and made 403 ft lbs of torque, selecting the components at 5000 max with a 5.0.
My engine - FTE, Cam 258 in/ 266 ex duration, .533" in/.544" lift, Trick flow 170 Track heat heads, Trickflow 4.03 forged pistons to match head, scat 393 crankshaft, roller rockers. The intake is a chinese copy of the eldlebrock performer with 70mm throttle body and MAF. It is meant to put a 351W under the hood of a mustang it will flow slightly better that 5500 RPM in a 5.0. Everything was selected to peak in a 5.0 at 5000 RPM or slightly above. The mustang tuner told me it wouldn't run worth a crap. But I had built similar chevy engines in the past and knew better. The tuner was still critical of the engine after he tuned it. Said I left a lot of HP on the table with the intake, cam and exhaust system, but then he added it is a hell of a lot of fun to drive and it will pick the front end up off the ground. His tune was equally geared toward WOT operation and I know he left a lot on the table in the part throttle operation. One day I will address it but it is still more fun to drive than anything I have ever owned.
I said all of that to say this. Keep in mind while you build. with 33.5" actual tire diameter, and my 700R4 set to shift at approximately 4800 RPM at WOT I am going 85 MPH at the 2nd-3rd gear shift. WOT in third is about 140 MPH at 4500 RPM. Sorry but I will NEVER go there. EVER! It gets stand still to the 85 in a hurry and had left more that a few hopped up mustangs at stop lights. But of course they will catch and pass at about 75 MPH, but who the hell cares in an Early Bronco. Selecting everything to max at 5000 RPM gives you excellent throttle response, you don't have to achieve higher RPM to get the same amount of torque and torque is what gets things rolling.
I run 4.27" R&P and its perfect for the 700R4 But i dont have the granny but have a slightly higher OD than your ZF. Honestly If I was going to run a ZF with 35s and the torque of a 351 FTE I thing 4.56 is about as low a gear as i would consider. But i think you would like 4.27s, and maybe even 4.11. My 393 turns about 2300 RPM at 75 in the 0.70 OD of the 700R4 with 33.5" and 4.27s. Your ZF OD will do almost the same with 35s and the same ratio. Your starting gear will be slightly higher but still about the same as the stock 29s with 3.54.
Also if you have ever had a large diameter tire blow out at highway speed on a short wheelbase vehicle you are in for a fun ride. That's why I stopped at the P255/85/16.
If you have access to a good lath and select the right 302 piston you could cut the piston to get the compression ratio down but ANY ford CI head will not flow enough to make the 393 reach it potential, BUT, it will still out perform the exact same built 351W.
People loose sight of the fact that CI will make more torque and HP across the boards when compared to the exact same set up of a lower cu in engine.
I have no idea how prices are now but when I built mine the trick flow track heat was the best option as it have rocker studs installed and no EGR passage drilled. You don't need massive flowing heads for a street/offroad Bronco, but the Ford CI heads just dont really cut it plus you get a little octane relief from the aluminum heads.
I was told by everyone, including trick flow, that the trick flow track heat heads with 61 CC combustion chamber and the trick flow forged piston with 18.6 CC dish would run just fine on pump gas in a 393. Well i guess that is true because 93 octane is technically pump gas and I have to keep the transmission in D driving around town because it if shifts into OD at low speeds it will detonate before downshifting. Again one of the tuner issues.
If you have any questions about building a 393 just PM me. I will send you my entire build if if want it.
