This is what a assume:
1. You are keeping the outside style frame brackets and are going to mount them on the outside of the frame.
2. You are getting new axle brackets to weld on to some new dimension.......with a 1 deg up pinion angle.
3. You are keeping everything else.
4. The "communications" you are now having are EMAIL. NOT phone.
5. You are NOT getting any new written instructions but are getting the axle dimension by email, NOT phone.
6. You are not getting any new written instructions but are getting where to locate the outside frame brackets by Email....or are you supposed to use the 24.25 rod dimensions? and drill all new holes in the frame.
I recommend taking off axle brackets. Carefully.
Now we have a third frame width: 55-59 is 34". The outside style frame bracket you have is used on the 55-59 kit. The axle bracket dimension for 55-59 is 36. (2" wider than the frame). So on your 36" wide frame, using the same outside bracket, the new CL to CL for axle brackets should be 38".
Ask what the new dimension will be for the new axle brackets to see if they have their act together yet. Let us know what they say. Don't tip them off to the number. If they don't say 38", have them do the math with you.
Can you reword this question you asked them. I have no idea what it says. "When asked if the frame brackets included in the instructions that came with the kit were available for me to exchange the response was as follows,"
Who is going to do this rework????
Does your frame measure 36" wide at rear????
This time mock EVERYTHING up. Magnets, clamps, minimum tack welds, whatever. Till it ALL looks OK. The coilovers and ALL.