Long story. I installed the rear diff on my 3/72 restoration. Later I found another new diff insulator on the shelf. The one I installed was Part #55415-E4102. Seemed to fit fine. I know now this insulator is from an early 240, and I must have had it in some old parts left over from another restoration. So I swapped the E4102 with the proper insulator, as I figure someone would likely need it in the future. As I scratched my head trying to figure out why both insulators seemed to fit fine, I started digging through some really old stuff looking for a diff crossmember to compare. I didnt find one, but I found this muffler part and I cant figure out where it is from. I thought it was the muffler hanger at the diff, but it just doesnt look right. I am thinking it might be from another car. 

I still dont understand the diff insulator. The one I ended up installing was 55415-N4301 which seems to supersede earlier ones, but not the the E4102. Maybe i just didnt realize the E4102 didnt fit, as I had not tightened the suspension completely, and its only about 35mm different. 

Muffler part:

 

Early diff insulator

 

 

 

I figured out the exhaust part, it is from a 79-83 zx. I must have grabbed it when I was robbing a zx of of parts.