If it was originally a GTS4 (i.e it is 4wd) it would be ENR33. I tried them all this morning, and no combination would work.
F = CA18
H = RB20
E = RB25
B = RB26
C = Super HICAS
N = Atessa
R = Chassis
CHASSIS CODES
-ER -- GTS25
-HR -- GTS
-ECR -- GTS25t
-ENR -- GTS-4
-BCNR -- GTR
Yes, if it says ECR, it is a turbo chassis/engine. The brakes are different, the number of wheel studs are different... i'm sure there are many other differences. If you had a motor swap, and you have a DE (Dual overhead, EFI) then either the plate is wrong, or the motor was swapped out.
So... if your chassis was a turbo model you should have 5-stud wheels, a stronger gearbox (not sure how to tell, but it could be a manual-only thing), obviously you'd have no boost gauge in the dash. The side-mount intercooler would have plumbed through the engine bay via two holes infront of the air filter box. That should be very obvious.
Check those things? If the chassis has all non-turbo parts, I would *guess* there is something wrong with that plate. Strangely though, that plate doesn't belong to another chassis... it just doesn't exist. =-o
Let us know.
-Steve