67-72 Build or Convert Gen 3 to Gen 2 HELP!!!

[blaked1516]

New to the forum looking to the near future and soon plan on building a 67-72 c10 and putting a 350 small block with 700r4 transmission.

I currently have a 1985 c10 (gen3) but I like the look of the 1967-72(gen2). Would parts be compatible like the hood, bed, grill, cab, quarter panels? Or buying 67-72 would be cheaper including brake conversion and other things that should b done. I already have a stock 350 and 700r4 in the 85 only bolt-ons would be needed.

I plan on bolting on some parts for performance: RHS Aluminum Heads, Hydraulic Roller Cam, 1.6:1 Rocker Arms, pushrods, and a 4 barrel demon carb with Edelbrock rpm air gap. This will increase hp by about 100 putting me at about 320-340. Stock transmission are said to handle 350hp but become less reliable around 3xxish hp.
Whats needed to upgrade the transmission?(I think I read something about shift kit and stalls)

What gearing is best for mpg and cruising at 70mph below 2400rpm but still being able to burn rubber and pull away when needed? (will not be towing a trailer just a quad and dirt bike at 500lbs max)

Is there any other information that would be beneficial to me?

Last question is if a buy a 67-72 c10 actually whats a good price point for a project truck with no motor or trans?

Your input would be greatly appreciated.