Dont know if you're still after any info for these engines mate but I may be able to point you to a couple of places and some basic stuff. First off changing the cams to the later BOB 24v ones will add around 20BHP, not alot I know but it makes mid range a bit better. You will need all 4 cams, sprockets and washers as you cant interchange the BOA and BOB washers as you'll loose tick over. A few people in the UK put in the Holden Vectra 2.5 V6 injectors? They reckon they work but I dont know?
I assume you know about Burton Power as most on here do. There is also Power Engineering in the UK who used to do a Ultimax conversion on these where it was bored/stroked to a 3.7 using a billet crank and all new innards. It was good for around the 270BHP but the torque was HUGE. The demo car they had would spin the wheels in any gear....lots of fun till it was written off in style!!!
I believe someone lost control, hit a curb and launched it through a hedge and over a stream where it landed in a field and bent!
There is Topboss performance (uk). They put the T5 in my car and I would never trust them again.....lots of problems and Customer service is unheard of but it is up to you.
Boost performance (chevroletls1.com)do a few upgrades too. Never used them myself but looks like good stuff.
As far as I know, the crank from the Explorer goes in with a bit of machining to the webbing for clearance and you have a 3.5 v6. As the 24v is a Cologne based engine and so is the explorer a few bits can be swapped. I am hoping one day to try this out but with 3 kids and a mortgage I reckon I'll be doing it when I retire!
Hope this is the kind of thing you're after if not then.....errmm....dont know really![88]
Good luck with it and if you discover some hidden BHP share it on here so I can sort mine out.
Cheers.