69 c50

[Pvmt-Pndr]

I posted this over a month ago apparently in the wrong section.
I'm looking at buying a 69 C50 with a small block 350, manual trans (not sure which one) and a 2 speed rear end. I have 0 interest in keeping the 350 in it. I was thinking of swapping a for a carburated big block and a 4L80E with a stand alone controller. My problem in doing this is the 2 speed rear end. The more I think about it the more I'm talking myself out of it. I would have much more torque then the 350 would dream of having but I'm not sure it would be enough to make up the gears to just run it in high. Another option would be to make the 4L80E completely manual and use low 1,2,3,4 then pop it into 4hi once I got some speed going. That sounds like a pain to me since I would be stuck in hi gear until I came to a complete stop again. Swapping rear ends is also something that is on the table too for something with a fixed gear instead of the 2 speed if there is a fezable option please let me know. Most of this truck will be one off when I'm done with it and disc brakes would be nice anyways.

I'm open for opinions on the best way to drop a big block into it with an od trans. If I do get it (I'm certain I will). It will be used to pull my wife's 72 Chevy mega truck around to local bogs and later will be used to pull a 40' trailer with 2 mega trucks (when I get time to build myself one) plus gear so 20k pound load give or take.

I've been doing a lot of searching here and fortunately the truck does have the 10 bolt lug pattern.

I'm debating an axle swap from a 4500 or 5500 truck so I would have disc brakes all the way around.

The truck currently needs a booster/master cylinder. Since they're only $500 I'm just going to replace the whole set up so I can drive it around. I will be upgrading that also down the road.