It wasn't until you said the front end was all fibreglass that I noticed the bonnet didn't have the centre ridge, then the added small side indicators. Wow. I mean that is some really nice body work. You have ticked all the right boxes on the 4G54 rebuild. I'd remodel the bonnet with a reverse air intake over the exhaust manifold side to vent instead of scoop. Heat is the enemy in these trucks, especially the G63B engine. The Gen 1's don't look right with a drop side tray on them, it ruins the lines of the truck. I'm in 2 minds of a custom grille. I'd like to do a full flush front end but I still like my chrome bumper (I picked up a wreck with a Volvo air dam grafted to the underside of it's bumper which is quirky, but works due to the Swedish brick being about the same width and similar body styling) A factory GSR would have twin headlights and a box section or honeycomb grille in black, a front air splitter lip with GSR on the lower right side and no chrome trim strips on the cab (they'd probably be black) The badges would be the same as Sigma GSR's - 2.6 GSR in red. GSR's come with bonnet vents or flutes. If you wanted to really up the ante on the 2.6 - hunt down Sigma GH turbo gear. It's neanderthal tech but is a completely different flavour of mental. My friends' GH in near stock form was silly fast...