3500 is wound a little tight, IMHO! Unless you've done a pretty good bottom-end overhaul, it won't last long at that speed. As speed doubles, the load on parts, such as rods and bearings, wrist pins, etc., SQUARES! Simple math will tell you you're getting close to some design limits at high speed. With good-condition bearings and weight-matched rods, I guess getting it wound up for a short time won't hurt, but I'd avoid extended periods of high speed, like interstate driving. I trashed a 58 model 235 with a leadfoot approach to driving about 40 years ago, burned out a rod bearing. I replaced the 235 with a 61 Corvette 283, and really abused the old car after that!
Jerry
