Nick, a 3 speed will suit your needs as far as a 2bbl and 326. If you go to a 4 speed, you will be hard pressed to get any pickup in first.. with a 2.52 first gear.
My suggestion?
Swap to a 326HO/350HO setup...IE 65 CC heads, 9.5 CR, 066 grind and a 4bbl carb. Change rear axle to a mid to high 3 gear (POSI optional) and use an M-20 Muncie. M21 is fine too, but expect to add $2-300 just for the 2.20 gear.
If you are at .030 over, you are close to 343CI .060 would be close to a stock bore 350.
If .030, run an 066 If .060, run the 350 HO specs and 65 CC heads.
I know I am rambling...but.
You will be severely dissapointed with investing in a 4 speed swap ($1-1500) without the HP to make it work.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
