I ran the magnum 270 in my 86 silverado last year with 3.73 gears, 700 r4 tranny and a stock convertor and it ran perfect in my opinion, I used a performer intake and a 600 edelbrock carb, it originally had 76 cc heads with -12 cc dish pistons but I needed more compression so I switched the heads to some 305 ho heads that were ported and polished and it pushed my compression to 10.3 to 1 , that really woke that cam up, it would pull hard from idle to about 5800. I wouldn't advise running that high of compression though, I'm just lucky it didn't detonate with compresion like that with a cast head, guess I did something right, the guy I sold it to says he's never had anything with that much power and torque that was so easy to drive.