Anyone else notice the last two six pics are of the Aussie inline Hemi six? I am curious if you have seen what it would take to adapt a tremec behind a \six and if you were looking at a new turnkey setup or adapting a used one over. If it were me, and I was building a truck with \6, I would look for a used Lakewood slant six bellhousing and a used Richmond Gear/Doug Nash 4+1 5 speed. Summit carries the individual gears to set up a progressive close ratio transmission. With that transmission, I would use 3.73 final drive gears, for give or take 2600 rpm at 65 with 31 inch tires. I would also plan on a hydraulic throwout bearing for the sake of simplicity. I am guessing you've already got a coilover 8-3/4? If not, then I would stay with the factory 8-3/8 (AKA 8-1/4) or 9-1/4 axle if you are staying with the factory width. Either one is more efficient and consumes less power than the 8-3/4, and you won't break either one of them behind the \6. I am guilty of towing a lot of things I shouldn't have with an 8-3/8 +NP435+ \6 '73 D100 and never had any problems out of it. On any crush sleeve pinion axle, it is advisable to use the Ratech crush sleeve eliminator. I wouldn't go through the hassle of coilovers either, I would fabricate spring and hanger mounts to use a Cal-Trac Mopar B Body kit, and even that's probably overkill for this combination. I would really be considering looking into a turbocharger build, I really think that's going to give the best performance for investment, and you've got a lot of room underhood to work with.