I'm using the RB 5port engine x12 with k-factory centax clutch and k-factory fuel tank. Stock mounts won't work for me because no endplay for the clutch bell also the clutchbell hits the chassis braces, and the exhaust header hits the rear, and top of the fuel tank bad with the rd- pipe, and the AE tank won't fit at all with the rd pipe.
I use 3 different engines on the car,with the same pipe and clutch set up,(RD pipe,and K-factory fuel tank,K- centax clutch, and to me there should be a happy spot for the mounting slots maybe where everything should work, with a chassis brace change,(leftside).. I'm sure Jay is on top of this. But with the first run of chassis's, it seems to me that you must make or find different mounts for each engine. But... The chassis is worth the mount problem!.
I never knew there was such a difference between engine manufactors before, but there must be. I mean we're only talking a few thousandths here and there.