You're asking the wrong person.
I think if they're left stock, you'll have a cheap, powerful luxury cruiser.
From my experience, the suspension would need a lot spent on it to make the car perform. It's not a stiff chassis as a base and it doesn't have tough suspension arms etc. They're designed for a smooth comfortable ride not fantastic handling. Luckily all balljoints, arms etc can be bought aftermarket for a fraction of Toyota's cost. There is enormous inter-changeability of parts between models with Toyotas, far more than I've come across with Skylines.
As standard, they have an open diff and composite universal/tailshaft joints. Manual box, LSD and driveline parts could be sourced from a Supra, and I've seen these cars converted to 6-speeds on Jap. auctions. Foot operated handbrake conversion would be difficult.
The under-bonnet temps are very high yet the massive radiator will not allow the engine to overheat even in the worst heatwave. The aircon is outstanding.
The stock heat shielding on manifold/turbos is excellent and to bin all that would need a LOT of thought.
As they're a RHS exhaust manifold, there's steering and brake equipment very close to the hot bits. Obviously this is why they came standard with the electro-hydraulic brake system which is extremely compact considering it also has the ABS incorporated.
Anyone who's fitted a 2JZ into an S13 knows how difficult it is to reliably keep the heat away from clutch/brake master cylinders.