Need help spending $4500 on 69 step

[casterbuster]

I have already finished the brakes, updated to power front discs. Replaced all stainless brake lines and hoses. Rebuilt front suspension. What the truck needs is engine, transmission, and A/c. 350 is tired loses oil pressure after warm up pretty severely. Trans is th400 with leaks everywhere. In the texas heat it needs a/c. It is a factory a/c cab but all components are missing.

Don't know if I should either add new crate motor or rebuild this 350.

I would like a overdrive transmission but this would mean different drive shaft different shifter and add more to the build. I could possibly just ditch the 4:10 gears and go with a 3:42 or even 3:08. What do you think?

Then where would be the best place to get the A/C kit from and which kit is better?

I need to get this thing on the road, I am without a second vehicle right now. The wife's Tahoe is all we have currently other than my company truck.