you're right- different size stub axles, different caliper bolt spacing, different caliper offset. and yes use the ZX strut on the 310 steering arm. Caliper will struggle to fit inside most 13" wheels. They only just touch the inside of my wheels, the wheels still turn though. (HRT learned the hard way that it's important to have enough clearance some may remember.)
I know all this as I have them on my bench at work right now. I'm modifying the 310 struts to have vented discs with skyline/300ZX 4 pots and all fitting inside a 13" wheel.
I'll let you guys know how I get on. I'm also making adjustable platforms and using really short adjustable shocks.