There are differences in some, in relation to where the solenoid sits, some sit closer to the block than others so will help clear your exhaust better than ones that stick out further., however theyre the same physical size.
smallport 4age's are smaller, well it was on my 1.
get it overhaul if you got the coin b4 you finish to turbo convertion as its an ass to get out once you put the turbo in.