A500 or 727 with GV?

Hey guys,
I have a 67 Dart currently with a 727. I was doing the calculations on RPM's and I'm going to be running too high for highway use unless I'm driving like 55 mph. So I was considering swapping to an A500 however, I read that the 727 was one of the best transmissions ever built and I'm afraid that the 500 wont be able to hold up to the abuse. I plan to have around 400-500 hp. Nothing super crazy, but plenty for street use. So maybe go with a Gear Vendor on the 727 which will reduce my RPM's by almost 1000 at 70 mph. Not to mention give me more gears than the 500. With the cost of finding a 500 and a rebuild on it + the mods that need to be done for it to fit I kinda figure the GV is the way go. What are everyones thoughts on this? Also, does the 500 even bolt up to a 360 motor?

Thanks in advance for the help.

-Mark