Phil,
I can only advise you not to do it, at the end of the day it is down to you.

I used to run a 34psi spike and hold only 26psi - my car would eat a T3/4 every 3 months . Pushing a T3/4 to 40psi is asking for trouble IMO. Don't forget that even the Grp A turbos were running maram shafts etc, and the WRC cars were running IHIs that are £6k a pop .

300bhp in an Escort feels slow as fuck . I'm telling you now, you WILL regret it .