I just went through this. Filled out the spec sheet for two companies. Ultimate and PTC. Never heard anything from Ultimate, got one sentence response from PTC. (8”, $950 plus shipping) was the entire email. Which tells me they didn’t really read the spec sheet I sent in. I loved my 727 PTC converter, so I went through someone who has a relationship with them and knows what I’m doing with it. I provided every piece of info you could have needed. I understand that they probably get sheets with “it’s a 1000 hp big block Chevy hemi” or “it’s got a 3/4 race cam” but when EVERYTHING is on the sheet, including a warning about the VERY small tire, what you want the flash rpm, you would hope to get real recommendation or at least a call saying “what are you doing?!?!?” I had every number off the PTC 727 9.5” converter and put it on the sheet and just wanted the same converter in a 904 with 200-300 more flash rpm. I love the 9.5” PTC I got for the 904. Flashes spot on! Slips 4-5% at the stripe.
