I ran a Pro4 at Halifax outdoor last year with the stock setup and it was pretty good but I changed to a 416 worlds for this year. Took it out with the stock setup for the first time last week on a damp track and it was amazing. So easy to drive with loads of grip.
I know its a different layout with different materials but there's a good chance the geometry should be good. I have quite a few tamiyas and the build quality is top notch. To bring it up to racing spec I'd want TRF Dampers and CVD's as a minimum so I'd factor in the price.
Ive got a 501x and a DB01, which is as good as my 501x, BUT its taken the price of a second hand 501x to get it that way so bear that in mind when hopping up a basic car.
I know its not giving you an easy answer but it might give you something to think about
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