Keep both if you can afford it. Garage the Rallye, use it at the weekends once you've got the charger overhauled. Keep the millage low and keep the body in mint condition.
The G60 engine is getting Rarer, so please keep it in the Rallye. Don't put a 1.8T lump in, you can put those in any car, why bother when you have a good engine already.
I'd love an Edition1 G60, but to have a Rallye too, it's just too much, that's greedy.
Do overtime, sell anything, organs, whatever, just to keep both cars.