Struggling on wheel size

[OZGMC]

Hi
I live in Australia and have a 94 regular cab short box 2 wheel drive and want to change up the wheels to 17x4.5 on the front and 15x10 in the rear I'm unsure of the drop as it was imported with it ATM have 20x10 in the back with 5.5 backspacing am running a full QA1 coil over in the rear so have the space

So the question is backspacing on the rear rims and biggest tyre size that will fit hoping 275 and up am happy to roll/trim guards
The hard part is I need Rim backspacing to be spot on to get right rim as will be having to buy from the USA or get Customs made as nothing is off the shelf over here

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[GoToGuy]

Use the wheel manufacturer web catalogs for wheel specs?
With straight across hub measure inboard, how much available? Good luck an nice truck!

 

[Orpedcrow]

This might be helpful

Thread 'Wheel spacing info for lowered trucks'
https://www.gmt400.com/threads/wheel-spacing-info-for-lowered-trucks.8950/

Might also be beneficial to put the truck on stands and take some measurements. Can also make a CAD model (cardboard aided design) with the same outside diameter of the tire you’re wanting to run to help you visualize the 3D space.

 

[Orpedcrow]

Thread 'Tire and wheel fitment tool'
https://www.gmt400.com/threads/tire-and-wheel-fitment-tool.60067/

This is another thread that is stickied in the forum, with this, you could buy the tires you want, take your measurements then order wheels that fit within those parameters.