I know my 67 engine bay is a little different than your 71, but my crites headers are tighter than a fat girls socks. I can barely slide a piece of paper between my shock towers and a couple of the tubes. If it wasn't for my front motor plate it would definitely rub when running
I have Crites Gen II headers & motor mounts in my '69 fb with uncut shock towers. It is a really tight fit but they do fit. A couple of the primaries make a downward bend immediately off of the exhaust port which can't be best for flow, but that's about the best you're going to get without either cutting up the shock towers and/or going to a custom header. 2" primaries are a bit small for my combo but the price was right at the time so that's what I have for now. Ground clearance is plenty acceptable for street. There is a specific order you have to bolt up the primaries to the head on installation...one way and one way ONLY. First time its trial and error. After that, no big deal.