Firstly you need to stay within (from memory) 25mm diameter of the largest and smallest tyres fitted by GMH to a HJ. The largest will probably be F78L14 however the only tyres available on 7" on HJ were ER70H14. You can get the dimensions of these on calculators online.

Rim width you can't go wider than 25mm more than the widest original available on HJ which is 7", so technically 8" is too big as it is 25.4mm wider than 7". But I'd say you would probably get away with this, it'd be a hard ask to tell the difference of 0.4mm!

Then you need to stay within 12.5mm of the offset of the original rims fitted to a HJ so your track doesn't change by more than 25mm. Original HJ rims have the following offsets:

14x5 and 14x6 except N66 Rally wheels: 0.63" (16mm).
14x6 N66 Rally wheels: 0.5" (12.7mm).
14x7 PE1 rims (honeycomb) 0.34" (8.6mm).

So as long as you stay within 12.5mm of the biggest and smallest offsets you are OK. So you can go between -3.9mm and 41.4mm and your track will remain within the legal limits, assuming you have a standard diff.

As long as you don't lower the car and choose the right wheel offsets you may not get scrubbing with those tyres. The trick is not to lower them - this is what normally causes all the scrubbing issues. I used to run 14x6 front with 215/65/14 and 14x8 rear with 225/65/14 on a HJ sedan and it never scrubbed and it drove really well.

If your wheels are 8mm offset the 7" should be sweet on the front as they will basically sit where a 14x7 honeycomb sits, and if the tyres are a similar size to an ER70H14 all good. If the 8" have the same 8mm offset you'll probably be OK too as you only have 1/2" either side of the 7". Just don't lower it much if any.

Edited by user Wednesday, 10 July 2019 3:22:16 PM(UTC)  | Reason: Not specified