Question about 944 Arms and axles

[DWP]

New to this site.
I am working on a modified sandrail frame. This is NOT for off road.
Plans are to lower for street use only.
Porsche 1.7 engine until i finish the 2.0 build.

I picked up a set of aluminum arms from a 1986 NA 944 with 5 lug rims.
Have to pick up the spring plates this weekend.
Shocks are no problem as I am making upper shock mounts.

Here is the problem. What length axles do I need?
At this time I have a 3rib bus trans. Considering a 5 speed in the future.
When switching from a type1 trans to a bus requires the use of Thing or Porsche 944 axles 16 1/8" verses stock 16 5/16 length to keep the ends from mushrooming.

Any ideas??

Dave