orench hows the weather there? never mind don't tell me.Anyway, last year i converted my 327 275 hp to a 4 speed, and i used a 11 inch flywheel and clutch. had a 10.5 flywheel in my 69 z and was'nt happy at all with it as far as launches. As far as my 327 wow what a difference! the 11 inch clutch explodes of the line, and has good pickup at mid/high range cruising speeds. i'm sure you will get other input to use a 10.5 clutch but i'm sold on a 11 inch. GM used a 11 inch in the ss350 cars. look at it this way, when you put the big block in, you'll be set up for it clutch wise. the best place to find a good used flywheel is probably on this site or some vendors such as Ricks, DR, or a new one from Summit or Jegs. good luck!