I have installed 6 new crate engines in various vehicles. I used Jegs and everyone has been satisfied. One was a 290HP and the others were 260HP. To be honest I didn't see much difference.
If you look at the specs the only difference is a higher lift cam. I have built and owned performance vehicles and in my opinion the more exotic you get the more problems you can expect. I converted my 56 from a 6 to a V8 over ten years ago.
Along with front disc brakes, power steering, and a 3 speed OD trans it is a great driver. I made up a list of the parts needed for the 6 to V8 conversion. I can provide it to you if it would help.
Fred