question rephrased

[duece05]

how much offset is needed for a 10" wide tire not to hang massively out of the fender well

 

[kleistang]

7.5"

 

[Miracle]

7.5"

That is backspacing.

A 24mm offset fits quite well under the fenders on these cars, if you can keep the axle centered as well with an adjustable PH bar.

 

[Hawgman]

My 10" wheels have a +45mm (1.8") offset and they fit flush. BUT... my 10" wheels also have the correct backspacing and from what you said in your other post, yours don't.