9 1/2" clutch.

I did a stock rebuild on my 273 with a slightly bigger cam and some porting on the heads, intake and exhaust manifolds. I would estimate 350. I don't know if Brewers modifies clutches but my local Clutchmasters does.
I had the clutch checked by them and asked if they could increase the spring pressure in the pressure plate. They can do that but he didn't think it was necessary for my build. Worse case I could have them hop it up if neded. Mine is really smooth and a pleasure to drive.