Since I started this, I thought maybe I should follow up with what I wound up doing.
I now have a rebuilt/upgraded 1998 Explorer 5.0 4R70W bolted to my Blueprint 408. 2000 rpm stall Hughes torque converter. 98 Explorer 5.0 harness that I reworked with help from
@EFI Guy and his well-detailed posts here. Reflashed Explorer 5.0 PCM with tweaks needed to run said engine.
The transmission retains the original AWD tailshaft housing, with the output shaft shortened 1" so it bolts directly up to the Atlas, no other mods needed. I used an OEM style Explorer 5.0 transmission mount and with help from
@ntsqd designed and fabbed a crossmember that goes over the top of the exhaust and front output, just like the OEM early Bronco design.
We started with a mockup made out of hardboard from SendCutSend that I glued together then used to check the fit. Next, made a temporary crossmember out of scrap metal I had lying around my hangar, so I could support the transmission while I worked on other stuff.
The SendCutSend crossmember arrived as a giant blister pack, some assembly required. The frame mounts required a second rev to get right, what ever.
On to the shifter. I used a Winters Sidewinder. I didn't want to give up my beloved Tuffy center console. So collaborating again with
@ntsqd, we came up with an extension, also with pieces from SendCutSend. The connection to the transmission required a lot of modification. Apparently some have gotten that to work with supplied parts, but in my case the cable wanted to go right through the transfer case, and the linkage at the tranmission wanted to hit the front driveshaft. You can't just angle the cable up because it messes up the geometry. Trigonometry to the rescue and I got that working, but it still barely clears at full front axle stuff. Still, barely clears is better than interference.
Some pix below.