Had a similar problem on my GTO. I ended up finding an aftermarket smaller high performance starter...that fixed the problem.
Cheapest first.....
I would start by adding some thermal barrier/insulation to the heat shield that you already have. Summit automotive has allot of this type of stuff.
Maybe double the heat shield by installing something on the pipe as well. Any type of header tape/wrap you can squeeze in is going to help. Summit again.
In the case of the 6.2 I am not sure if a smaller starter is a viable option.
Have you ever replaced the starter...? It is possible that you have a weak starter that is heat sensitive.
Hope this helps, Good Luck!
1996 Chvy 3500 CCDWLB 6.5 Heathed, NO vac, marine injctrs, ARB bumper, BIG pipe, 3" lift, bright lights, bypass oil system.
1986 Chvy 6.2 M1009 blazer RAM AIR, Headers, Custom interior
2001 Chinook RV, V10 gas
1974 John Deere 1530 diesel tractor
1993 John Deere 455 Diesel lawn mower
1967 GTO, 1989 Honda Transalp
2009 VW Jetta TDI, flashed and piped, 6speed, fun car!
1998 6.5 suburban, stock, daughter's
1993 6.5 3500 CCSWLB GM8, Heathed, big exhaust, gauges, Son's
1984 6.2 ATS turbo 3500, SCDWLB - Son's
3 kids, 1 wife, 1 dog
Gunsmith, Tactics Instructor, Fabricator USMC 87-93 Semper Fi!