I wanted a nostalgia build and something different, so I put a 348 in my '48. Here is a link to my build
http://67-72chevytrucks.com/vboard/showthread.php?t=592642 It was easy and no cutting was required to the frame or inner wheel wells. I would recommend trying that forum and starting a build thread. I would enjoy following along on your build. The only problem I had was due to setting the motor too far forward and it interfered with the radiator. I just moved the rad forward and am combining a Chevy rad support with a GMC to remedy it.
Here is a good site for additional 409 info.
http://www.348-409.com/forum/
