I had this same thought for my PV that is in need of engine work. I didn't know Chevy made a 60 degree V6, what cars are they out of? There are some pictures and story somewhere around here of someone who put a Buick V6 in a 122, but I think it was a 90 degree V6 and therefore interfered with the steering column. That person solved the steering problem with a series fo u-joints that looked pretty scary. To avoid problems like that I was looking into a 2.7 L Toyota Truck four cylinder. It has a 16 valve head that puts out about 150-160 HP. And they are still in production when I checked last. Also, since it is a truck engine there are plenty of them available in junkyards that are connected to a manual transmissions. I decided that it would be better to have a manual tranny rather than deal with the computers that run automatics. In my case, these ideas are just in a dream phase. I haven't actually found one of these engines and measured it.
Tom