Had a similar thread not too long ago to this and I posted this:
For 4wd the Associated B44 is a good car for these reasons: parts are usually available trackside and it's a popular car amongst club racers, setup advice is 99% of the time always available and people will be able to help you with any problems etc and can be picked up from this forum 2nd for around £130-150 with a few spares etc and if you want one new they are still a really good price compared to other top end 4wd cars on the market and you don't need any upgrades for it as it runs great right out of the box!
Theres alot of 4wd cars on the market now and not going to write huge essay on them all as there are so many on the track that are all matched for performance now so the best I can say is choose which you like the looks of best and go for it! No car is the best!
Good 4wd contenders from the top of my head that are easy to get along with are:
Associated B44
Hot Bodies D4
Kyosho Lazer ZX5 sp
Schumacher Cat SX
Yokomo Bmax4
You will need a motor and speed controller, I recommend a brushless setup it's the way most people have gone now.
Good brands are LRP/Nosram, Novak, Speed Passion..., 6.5 or 7.5t motor is what most people use now,
A servo preferably metal geared and atleast .12sec/60deg speed or quicker with around 7kg torque or more,
Battery to power your car and a charger suit, lipo's is the in thing now... plenty of brands out there to choose from and you will only need one pack, just keep charging it up after each run. Some good brands to get these are trackpower, lrp/nosram, core rc, orion, reedy etc.
Think thats about everything, the popular tyre choice for indoor carpet tracks is schumacher minipins and minispikes in yellow compound
Hope this is of some help to you
Best regs.
Mike Hudson