unless its been ported it should be 87mm. as far as adapter blowfish racing adapter will allow a stock gt350 tb to mount to a 6.2 intake manifold, atleast on my 250. i was going to use one of these in conjunction with other mods. the tb and adapter are sitting on my garage shelf. i have also read that tuning for this throttle body can be a pain on the 5.0 depending on the year.
Would you snap a pic of the adaptor and post it please. I searched for an adaptor but came up empty.