I personally have a thing for the SC300/SC400 body style but I will give an honest opinion.
Since you already have a mk3 it will be cheaper no matter what you do, whether it be build the 7m, or drop a 1jzgte or 2jzgte into it. cheaper. Now if you dont care about cheaper and you Really want to persue the SC300 setup then you can go two ways. edit:: It will cost a lot more going SC400, so don't bother unless you stick with the 1uz.
But with the SC300 you have three options.
- 1jzgte full soarer swap. You either buy a clip or motorset with the soarer R154. You need the wiring harness + 5spd ecu and it will be plug and play inside, but you need to lengthen the wiring harness about 2' from RHD to LHD configuration. Mk3 R154 front driveshaft, lsd rear end out of a mk4 or soarer/SC300, and a few other tiny things.
- 2jzgte full swap. Pretty much every thing that is mentioned above, except the 2jzgte wiring harness and ecu will not be plug and play and you will have to have your stock wiring harness and 2jz wiring sent to someone like dr tweak to be matched together. This setup will cost you more money than any thing listed here.
- 1jzgte head or 2jzgte head on GE bottom end. If you go for the 2jzgte head, you will have to deal with the wiring issues mentioned above, so I will just tell you whats involved with swapping the 1jz head on. You will need to either go single right away, or use the stock twins that will blow soon because you will overspin them on a 3l setup. Need all of the intake setup from the 1jz, Mk4 TT oil pump with sensor, need to drill the block for an oil return and get the Mk4 TT union bolt (95+ I believe) that is tapped already for your oil feed. You could buy the boostwerx or boostlogic oil line setup if your going single that cover all these parts but its about $200. 1jzgte soarer wiring harness and ecu, you still need to extend the harness 2 feet, thicker head gasket to drop your compression to 8.5:1, upgrade to 440cc 1jzgte injectors, or 550cc 2jzgte injectors with the resistor. There will be 2 gauges that will not work on your instrument panel, I believe one is your tach and the other is water but dont quote me on that. To fix them you need to cut a wire and ground it to the chassis to fix the water temp, and the tach needs a resister soldered in. This is the setup I am going to do some day, I feel for street use with a correctly sized turbo the 1jzgte head mated to the 3l bottom end will provide excellent spool and streetability because of smaller ports in the 1j head, though it will choke out at around 600rwhp and need to be upgraded (cams, larger valves, port?).. Correct me if I said anything wrong.
Take the engine out of the SC 300/400 and put it in the MKIII 