[HO455]

You will need to determine what axle length you currently have to start.
When trying to fit the largest wheel possible you cannot rely on measurements from a different vehicle. There are too many manufacturing tolerances that can stack up and what works on on vehicle won't work on another identical vehicle.
You will need to mock up the tire you wish to run using a wheel fitment tool. They can be bought, rented, borrowed, and if your handy, home built using metal or wood.

Once you know exactly how the tire fits in the space you can then determine the best offset of the wheel t fit the space. Then you can determine how much you need the axle shortened.

I recommend looking at the Mark Williams website for more information. And if you need more information give them a call as they have always been very helpful.

https://www.markwilliams.com/tech-index.html

https://1320wheels-com.3dcartstores....Kit_p_147.html

https://www.rsracing.com/TechWheel.aspx#fitting