Are you sure they did that with a T51RSPL? For some reason I thought they were on a GT45 or even 47R Garrett which given the level of performance of the car may have even been a special version.
Spent a little while then searching around; Yes GK and SPL are similar, GK has higher HP rating for the same level of response. T62R was made to (apart from other things) nudge out the GK, and naturally is bigger. The thing is though, for this discussion the SPL really isnt needed IMO, here's why; Garage Saurus using an old 34D ran in the 8's, so that's got to be enough power for Chris to enjoy .....or is it haha
Everyone here's 8's, 34D, Watch from 1.12.
www.youtube.com/watch?v=CumKizAuuDw
I did ask him which rear it had when at his shop but it was ages ago and I forget. NYTSKY might remember, he was busy buying a bellmouth at the same time