can anyone tell me what model porsche parts fit an IRS/balljoint beetle, as in gearbox, trailing arms and brakes?

The 944 trailing arms and disks will fit straight on but you will have to modify the drive shafts. From memory the turbo has better brakes and stronger cv's Be ready to bend over and cop it as the prices are a bit high. Porche-a-part in Melbourne can give you some idea.
The early 911 5 speed box will fit but i think it involves a lot of modification.
Hope this helps.

Todd

924 turbo is the same as a 944 (pre 1986) they have single pot 12'' ventilated front and rear with integrated handbrake. The later 944's had twin pot calipers but the rear trailing arms are alloy and increase track like 76mm a side compared to the earlier ones (24mm) They do look tuff though The front end needs a ton of work to make happen, either way its expensive unless you have a friend with a cnc lathe. As far as box's go you've got three options: 901 froma real earlie 911, weak as piss a 914 from a later 911, nice choice but loads of work to fit.....so why not bite the bullet and get a G50 from a late 80's 911. I've seen them as cheap as 3k if you look hard but they will hold a honest 600hp without complaint Ask Reub if he likes his