There will be some good input here I'll bet.
With all the comments you'll get the old saying holds true: "there's no replacement for displacement"...
IF you can afford it definitely go with the aftermarket block. Several reasons why it is by FAR the best choice...course you are talking about a $3,000 additional cost to a stock 351W roller block so they'd better have some benefits!
Much stronger block
Much more steel around each cylinder (look at the outside of the block and notice the bulges from the castings whereas the stock block is smooth on the outside). More steel, more heat transfer, stronger- all good
- main brg web areas are stronger (meets the "stronger block category-many examples of areas within the block that are stronger but I won't name the areas I know of)
Smaller main journals- much more important than many think. Less heat build up from the oil/brg surfaces...makes a HUGE difference when turning high rpms for extended periods
- HUGE difference- within the past 10 yrs or so it's becoming evident that the stock 351W blocks have cracking issues btw the #2 cam bearing casting and the valley...always pull the brg out and check for any crack before buying or building.
ALL aftermarket block strokers cool easily...I've been doing very informal survey's at every Bronco event I go to and I have never found one aftermarket block 400+ stroker with cooling problems (unless they have really "tried" to have cooling issues (no shroud, smaller than stock or 15 year old crusty radiator, etc).... whereas many 400+ cube strokers based on production blocks at times or all the time have cooling issues... this is where all the extra steel and different water jacket design is superior in this area also... example: my buddy's 454 SBF cools easily with a 12" electric fan! No joke! he has 2 (one in front and one in back) but might need both 1x/year.... (we have many 90-95 & 100F days.)
Dart and World Products seem to be the leaders in SBF aftermarket blocks for 400+ inch strokers.
I built a 418 based on a production 96 roller block. IF I could have afforded an extra $2800 8 yrs ago when I built mine I would have gone aftermarket block. I had spec'd out a 427 for several years in advance but when I was ready to buy a crank I could not find one in the USA...Seriously, they were out of production at the time
I couldn't believe it so I built my 418. Less clearancing on the block, etc...but I wanted a 427.
No reason to not run more cubes...2 years before I built mine I spec'd out a WP 454 SBF in my buddy's Bronco...still running great. I would have loved those cubes but $$$$$$$$$$$$.
You will never look back and wish you had less HP...there are many times when spinning my 40"s for several minutes at a time above 5,000 rpm that I wish I had more power...just last week in deep snow for over 2 miles at appr 15% incline in 24" heavy wet snow... Yes, 2 miles at that min incline the entire time at 4800-5400 rpm... supposed to go again Saturday.
Have fun, build it...
Hard core off road = EFI I run Moates tune based on Ford SEFI but there's other options but not for my type of wheeling.
Street and trails but no severe off road angles (for big strokers) = Quadrajet (no other carb out there can do what it does for street and trails. My buddy's 454 never hesitates with his 800 Qjet but he doesn't do Moab, Rubicon, Fordyce, etc... my disclaimer for the Qjet with 400+ inch stroker is the fuel demands...I tried for several years to dial my Qjet in for the same performance I got from it with it in my 351W... but I couldn't.
I could crawl almost on my side OR I could shift at 6K in second gear and twist off rear end parts but I couldn't do both...either/or with the Qjet on the stroker
