Really depends on tyre/wheel combination also if going coilovers or just moving shocker to rail with tubular lower arms & how low you want can change clearances drastically.
Safely will fit 255/60 on 8" rim & have it sitting at nice ride height etc...can go 275 but lot more work & hassle for effort ends up sits higher than you want & rubs....main reason most chop into rail.
Deep dish fr1 20x10 is coilover job...can probably jam deep dish 15x8 not sure on offsets but most likely 245/60 to keep it sitting low.
Most sensible approach 20x9.5 narrowed diff & tubular lower control arms work...side benefit can swap back to sle rims to change look.
Split tubs + narrowed diff is not as flash coilovers & tubbed but heaps easier for rego or defects & if keeping car long term you'll regret doing mods that can get a car kicked off the road or not reversible.
Funniest thing is most of us who have tubbed our cars start to miss the classic look of small sle rims lol