Just I‘ve got a (new 2018) Plus4, but got the Rover Plus8 bug. And I was always in old MINIs.
If you got a old car, keep it, drive it and: love it to use.
So some changes are an option. But they must be easy to do and easy to build back. And if you have a look at the car: it must be done very secret. So far some easy points.
But on the technical side: there are a lot of modern cars around which have problems to handle with torque.
Not the (sometimes massive) power upgrade is the problem. The torque. Have a look at the technical datas of the MAZDAs and
their torque diagram.
As I‘ m in MINIs I always love the 1000. Underrated, but cheap and most with a good gearbox. I‘ve got komplette engines with gearbox
for 20,-EURs or „oh please collect it“ a few years ago… the same gearbox as the 1300. But the 1300gearbox? Most with some problems.
Greets René