that white site is a decade old
terry houston made pipes generally they were 3" SS but also built a few 3.5" and they fit perfet and worked without issues period, he isnt making them and hasnt for almost a decade
the terry houston design has stuck as the name to describe any pipe that has the same appearance of houston pipes with the wastegate puck in the flange of the pipe which eliminates the stock cast elbow .
atr , ,mease , TA , red, GN1perf gbody, rjc and others made pipes over the years that are technically terry houston style
atr (out of business) ...the pucks were 1 3/8 but had sticking issues , the pipes fit well
mease (still welding but not making buick stuff right now) made some nice ones and his came with 1.5" pucks
gbody , gn1 and others had a shiny off shore stainless version but pucks were too sloppy
the rjc is the only terry houston style pipe that i know of thats still available for purchase new
all the others including one from terry you'd have to find used