You can use regular length yok springs. I ran pink front and blue rears in VTA. And I believe I went with fairly small spur. 76-80t? And a 50is tooth pinion. The internal is 2.5 so depending on motor you want between a 3.7 and a 4.5 for VTA
It makes a pretty good VTA car. Just be careful of the doffs. They need rebuilding with new parts every 3-4 full race days. Otherwise they just let go unexpectedly. And after the aluminum c hubs, mine was pretty bullet proof in VTA.
Have fun and enjoy the car.