The block on the newer (L22?) 194/230/250 style sixes may be smaller, but from what I understand, the water pump is longer. Going that route will likely find you moving the radiator forward. I would stick with a 235, or 261 if you could find one, with the bell housing that will bolt to the existing frame with the side mounts. You'll also have the single front motor mount right where it belongs. Try to find one of the old three speed Borg Warner overdrive units, they pop up on E Bay from time to time(The Saginaw version was made thru '87). or even look at swapping in a T 5 from an S 10 for overdrive. I'm pretty sure you could get away without any crossmember problems that way. I think the '46 rear end was slightly narrower than a '67-'72 rear end, but not sure, you might want to do some measuring.
