A GMC oil pump is much larger than one for a Chevy- - - -which would probably involve some oil pan modifications for clearance. Another option might be to use some type of dry sump oil system, with an external pump driven by a Gilmer belt. NASCAR has run those systems for many years, so parts are available. That would supply plenty of oil volume to lubricate the engine and oil/cool the turbo. The high oil volume is needed to keep the turbo bearings cool.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!