i put a underbed one on my 63 and my 64. i didn't have to move any of the larger crossmembers or anything like that. i got a poly kit off ebay for one, and a steel tank from lmc for the other one. both were around $200 several years back. i have heard of people using junk yard tanks, but since i had just rebuilt the engine on both of mine, i didn't want to take that chance.
