Hey Bret - Not Blue thunder caps but
There is a company in St. Charles MO who makes main caps that appear to be very similiar to the blue thunder caps, so much so i questioned his patent pending? considering blue thunder has been making caps like this for years.
Note -I have not used these caps so i cannot verify the quality but i beleive Dave McLain mentioned this allied motors in conversation back in 2003 at the engine masters contest.
Blue Thunder is no longer building the caps. Dennis at DSC has the last 6 sets that I know of. I just bought a set from him to install for a customer. I may start building caps if BT doesn't start back. FWIW, the BT design came from Engine Systems. They decided not to build them anymore and gave their dimensions to AT Francis. That is per Ted at ES, 3 weeks ago.