They have made them for about 3 years. They are designed for an Monte SS but can be used for a Gn or a T.
the upper half has 2 vertical lines. Slice the upper seat bun for the location of a GN. Then glue the 2 pieces of pre sliced foam together.
The lower bun has the corect spot for a GN. a T will have to be cut further back towards the top half of the seat to be correct.
We plan on running a seat cover & foam special in June. Where you can add the seat bun for $150 a side or both for $275.00 with the purchase of a set of seat covers.
We actually blast the seat frame & powder coat the frames for our personal cars. Looks great when it is complete. No more surface rust on the frames.
I used the neat foams from G Baody...Pricey and restore lost cushion for sure. I dont think they are quite as dense as factory but do a good job. Had them in for a yearish now.