I've seen this problem with early 4V heads. I can only relate what I've read as I've never had this issue, even though I have early 03 heads.
The real problem as stated prior is the lack of threads on these mod motors. I don't think over torquing is your problem, its just inherent. I've always torqued my plugs with anti-seize to what feels like a ring washer sealing. These dudes aren't re- threading your heads but, inserting a helicoil to solve your issue. I would just get some really late, or aftermarket heads wit more threads and be done with it.
03 Mach 1
Kenne Bell 2.1 Stock block, built 4r70w w/ Fairbanks, Accufab, SLP, Moser, 3.73, Trick Flow, Magnapack, Megabite Jrs, AFS
1/4 firstname.lastname@example.org, 1/8 7.4@95 on NTO5r dr's.