My '67 04B LOS L35/TH400 uses the straps and round radius rod.
The '67 05B LOS L35/M21 uses U bolts and has the square radius rod and additional bracket w/snubber pad.
Based on past CRG discussions though, I believe there was a difference in the front and rear yoke angles, relative to each other, between a small block and big block due to the difference in motor/transmission offset?
Mike