the exaust wheel will have only ten blades on it
the 52 is the same 10 blade
all others i have ever seen are 11 blades.
with each pass faster than 11:50 it will most likely have even less blades.
it should be scratched into the intake housing where the i/c hose slides on it and stamped on the exaust housing where the elbo/downpipe bolt to it.
i would tell him to get a ta49 or te44 before getting the 51 you can go faster with a te44 than a 51 and it will spool better and will definatly outlast it.