What clutch are you using on your early 273

I ran a Rayloc 5004HD from NAPA for many years and many miles. That was a 10" Borg & Beck style for direct replacement of the 9-1/2" Auburn clutch that came in the early 273 cars. It had an organic disc. When I put a 340 in one car and wanted to retain the 122 tooth flywheel I called American Powertrain and they put together a really nice 10" diaphragm style with organic/ ceramic disc to hold the additional power, which it did nicely. Unfortunately I didn't hang on to the paperwork that it came with so I can't provide the part numbers but if you call American Powertrain they can probably fix you up with something very similar.