My next project is to try and correct the Nitto / Blue Tank M4 High Speed Tractor. Can anybody help me out with any serial numbers, sites, photos or any useful information.
Cheers
Kevin

Kevin, that will prove to be quite an undertaking if you choose to take the "full-kit-correction" path. There are quite a few problems with the kit that need to be addressed if you want an acurate kit. Go to the site by Cookie Sewell for a descent article on this.
I have the kit too and have not gotten the courage to delve that deep into correcting it...yet. Perhaps if you do, I'll follow suit. Either that or I'll just hunker down and buy the P.S.P. kit.

Here are a few sites of the model and the actual M4 HST:

M4 HST - vehicle close ups
M4 High Speed Tractor by Steve Zaloga - I believe this is the P.S.P. kit.
TRACTOR, HIGH SPEED, 18-TON SERIES - actual vehicle
Nitto's Corrections article by Cookie Sewell - aticle on correcting the kit

Good luck and please let us know how it goes.