I use the Mr.Gasket Ultraseal header gaskets with zero issues, I even re-use them 2 or 3 times.
I tried RTV only once and didn't like it but alot of guys do it that way. I thought it was hard to get the headers on w/o damaging the RTV surface and it was no fun to clean up the next time I removed the headers.

1970 Challenger, all aluminum 528 Hemi, HDK suspension, Tremec 5 speed manual