I think slant six's are cool as hell. But since all the real knowledgeable guys are not responding I will try in my noob way. Motor mounts aftermarket maybe will work to modify it. You will need a different tranny with the correct bell housing size. Maybe a modified drive shaft ,,shorter or longer.
Then all the other stuff ,carb linkages ,radiator to keep the 440 cool ,,,hell I don't even know if the big block is in if you have room for power brakes. Actually I am doing you a favor because I am sure much of what I said could be wrong and now the guys that know will chime in!!!
Ask your friend what the hell is wrong with a slant six? Is this a drag car? I hope the guru's will enlighten you,,,,,,,,,,now lol.