The RWD setups came out in import AE86 Sprinters, Levin, Trueno. The front wheel drive motors are ok at a pinch if you don't have to use the standard inlet manifold. If you don't want to use the computer and injection it is quite straight forward to fit twin sidedraughts but you will need to change the distributor...I think a non injected corolla dizzy can be made to fit.
Engine mounts were quite easy to make up. If you're wanting to have it certified then all the welding will have to be done by a certified welder.
Brakes and front suspension will have to be uprated. I am using bilstein suspension and 4 pot AP calipers on the front with discs on the rear. I use a pedal box to alter bias from front to back, something that wouldn't be required on a straight out road car.
Gearbox is a T50 splitcase which is used normally behind the RWD 4AGE. In the Toyota they use a hydralic clutch but I have adapted mine to use a cable clutch, using the standard Datsun setup.
There are many different transplant diff options that people are using in 1200's. There is no way that the standard 1200 diff will cope with the 4AGE. Even a C20 diff would be borderline. Have a look around this site and others and work out what diff ratio you need before deciding which way to go.