The first model TT (white/red tank) ran a steel swingarm. '77 and on (orange/alloy, yellow/alloy) ran an alloy swingarm.
Yes TT's had a lighting coil, so you can run lights.
XT/TT's have a massive steering rake, so don't handle that great. (They do in a straight line.) White Bros made offset triple trees for them in the '70's or you can cut the rake back to 26,27 degrees if your handy with a torch.
Sand riding, get it up to 60-70 mph to stay on top of the sand. Any less and your just ploughing. Beach sand is harder than desert sand to ride in.
XT/TT 500's do awsome wheelstands.
Bought a 76 TT500 when I was 16. Only bike I ever cried over when I sold it. Bought a few XT's years later, sold them and regretted it. Finnaly after 23 years of searching, stumbled across a 76 TT500 in original unmolested saftey stickers still on tank, condition at a swap meet and fell over myself to get it. One of the sexiest dirt bikes ever built. Have been collecting period after market bits for it on ebay.
A fully restored white, orange or yellow TT in Australia pulls about $5-6,000 au.