From what I recall, B Team Race wasn't all that popular to begin with, due the the mountain of rules. Then in 1964, somebody got what was effectively a B Proto Speed to work and went about 130, thereby really killing the deal. Henceforth, Rat took over. Fewer rules & more power.
Using a 29, which was a dying engine size, was a huge nail in the BTR Coffin. 40's were plentiful and faster. So why knock yourself out looking for a 29 that would hot start?
F2C's, with readily available 2.5 cc engines have become the standard of the world, and quite rightly so.
I was given a BTR and I fixed it up ready to fly. But then I found that it has been disallowed by the rule aimed at busting the "120 MPH" racers. I would be surprised if this one does 90. I looked re-engining it, but the mounts are too narrow for any 29 that fits the latest revised rule.