1970 Camaro - Mini Tub Desicion Clarification

[68LS1]

I've just purchased a 1970 Camaro project, here locally in Oz.

I'm pretty sure I want to mini tub it. It needs quarters and outer wheelhouse replaced due to someone making way for some bigger tires. Could be mistaken for a Vette from underneath, there is that much fibreglass involved.
This would seem to be a logical time to install the mini tubs.

I haven't made up my mind on suspension, this may depend on engineering for registration, but thinking a coil over set up most likely.
So initially I was thinking of going to go with full kit with leaf spring relocation. But this may been frowned on by registration here, as from what I can make out there are frame rail mods required and a narrowed tank.

So if I just install mini tubs at this stage I leave my suspension options open?
No frame rail mods?
Can still run full width fuel tank?
Can use stock leaf spring suspension initially?
Minimal gain in tire width (until aftermarket suspension done)?
Will still need to mod back seat & rear interior panels?
Rear seat belt mounting point relocation?

Are there any issues/benefits I am not considering by going with just tubs at the start?

thanks