No offence Mcklaren, but I am not triing to sell a car.....
Yes the standard XXX-S can still compete, however it will be at a slight disadvantage due to weight, and the fact that there are several very important tuning options included in the G+ kit.... if you can gt the car for say around $150 with threaded shocks or $100 w/o the shocks the car will be worth it because you can upgrade to the graphite kit and come in under G+ kit costs.....
You know what they want for the car and you can find the value of the hop-ups on-line.... see if it seems worth it to you.....
Remember things like Yellow belts, and titanium turnbuckles can be replaced as the old parts wear out....
With that being said I am sure MClaren's car will be a great deal, but I would say he still wants a nice chunk of change for it..... However I am unsure of what he is looking for....