HMM, get a chevy TH350 auto trans, your SBC wont bolt to that chrysler 3spd, motor mounts are diffrent but easy to change. I didn't know chrysler had a flathead V6, really, they had a flathead 6, or inline 6, commonly known as the str8 6. All cylinders are in 1 row and theres only 1 head, a V6 would have 3 on each side with 2 heads and 2 exzaust manifolds.