I have not seen Kaiser Bill's frame splicing but I have 2 comments about such proposals.
1) 51-55 Kaiser frames are not as solid as you may think. In 1947, KF had problems getting steel and I think the big crush was special steel such as would be used in the frame. Get under a pre-51 car and a 51-55 car and compare the frames. The 51-55 frames are less substantial, but lighter and used less steel. Jack up a 51-55 car in the wrong place and you will dent the frame rails. This project isn't just remove the front clip and shove the stub frame underneath either. There may be more bracing required than you think.
2) You really haven't measured the track (width) of a 68- 74 Nova stub frame (67-69 Camaro) have you? I have seen a 50 Ford, a 54 Kaiser, and a 50 Kaiser with the GM stub frame. The wheels, even with a generous negative offset poke out the wheel openings.
If you really want a modern suspension, you should consider using the whole chassis from a 1977-87 GM B body car. At least 2 members have done this and the results look quite nice.