the 1500 will present a major problem if he wants to use Reverse.
the 1800 found in a slavage yard will be better.
like the one that I got my spare parts from, it met up with a stopped car.... front end a total loss, from the triple tree back, it was like new. the 1800 has Electric Reverse.
for me, that thing spells Sweat Box, no ventilation, and for sure, no a/c.
I don't see why the 1500 would be a problem, mine has reverse. the GL1500 came with reverse on all but the Interstate. The parts bike I have has reverse and it works fine.
As for the sweat box, that is why I said I want to build it as an open cockpit style, convertible, just a windshield and a roll bar. No roof, no side windows, open air. More like a Slingshot, but with the engine in the rear.