Either block will do the job. We do a lot of these, for many different applications, but the most popular one uses Edelbrock D-ports and a hydraulic roller in the 400 blocks. Either route you go, a true 85 or 87cc chamber with these combinations will require the flat top piston. Which generally equates to 10.1-10.25 compression. Even at 10.5, still NOT pushing the limits, is perfectly fine IF the cam profile is correct. That goes for any compression ratio, even with less compression. It's all relative. Butler sells good rotator kits, we get ours through Liberty from Eagle, with the Mahle pistons 1, 1, 2mm ring set and we balance ourselves. Hope this helps.
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