the 1970 trans is likely the sm465... the sm420 predecessor.
I won't say it can't be done, but ... You have your work cut out for you! I steer away from trucks that have the 350/TH350 swap. You never know what was cut out of them to make it work. As mentioned previously, you will be missing a crossmember. If you have decent metal fabrication skills, this won't be much of a problem. You might be better off flipping this truck and getting one with a 4 speed, or 5 speed, or 3 speed with OD...
Part of the fun is building them. I just don't enjoy fixing previous owners eff-ups.
