Spring Plates? Where to buy? Hard to Fab?

70 Dart, Leaning tower of power right now but I have a chance to get a 8.25 rear end with bbp for 300.00 with sure grip 4.10s complete. The guy wants my spring plates so he can put the 7.25 that I am swapping him back in his car to drive it untill he puts his 8.75 in his dart. He wants to keep his spring plates because they fit the 8.75 also. Where do I buy spring plates? I saw a referance to the mopar catalog but without a part number or make and model after 1986 they can't find them at the dealer. Any help would be nice. Also is 300.00 with my 7.25 rear end also a good deal?

Thanks in advance. Mopar kid for life!