When upgrading a V8 you gotta be real careful on 2 parts. and be warned that if you end up cracking a gearbox you are gonna be S.O.L due to the fact that the V8 is based off of the V2 but it is different in a few ways that makes it nigh impossible to get it to work right with the selector switch and burst-mech, that being said lets move on to the 1st thing you need to be careful with.
1. The burst and selector switch,- Unlike other Marui guns that had a 3 round burst this one is mechanical (Sig 551-550 using a circut board) and the more wear you put on the gearbox the least you should use burst. A problem I have heard ppl running in to is causing your gearbox to lock up more than usual when it is on burst mode when it is upgraded due to the rifle wanting to pull but it dosnt have the power too if your battery is low.
<===thank you sekiryu
2.It uses a non-standard trigger switch (it reminds me of a inverted V2 is slides up and down to make the connection rather than side to side, shown in the pic below), be careful running a larger battery like a lipo or removing your fuse.
If I was going to do a V8 project I would make it more durable than performance based. I would start off with the basic shell and build from the ground up replacing everything that could be problematic such as the stock wiring and all low end plastic parts, all of the parts for a V8 are almost identical to a V2 so standard parts will work you just have to watch out about its few quirks.
--Parts list--
Deep fire metal air nozzle
Systema polybarb piston
Systema bushings
Systema piston head
Gaurder ball bearing spring guide
Gaurder gearset
Madbull 130 spring (440 fps give or take)
Promethious/Deepfire Tightbore
Systema bucking
AMP motor/G&P motor