You DON'T need 12.5:1 and you DON'T need a Hemi to run 10.90's. Plenty of guys in big heavy B-Bodys running those number w/ old school 590 solid cams and low-buck 440's. I'd probably run a newer grind or a solid roller. I'm running a 588 comp cams solid roller. I'm guessing it cold run 10.90's if I made a few changes, like swapping my 1 3/4" headers for 2" pulling the factory 6-pack for a M1 and 1050 DOM, adding cal-tracs and jumping from a 3800 to 4200 and changing my 3.91's to 4.30's but I drive it to and from the track, and all over so I like it the way it is. I will be adding the headers this winter so we shall see how much that helps.
If you are worried about compresion you can always run a $300 snow performace meth/water injection kit... it works!