Differences between the A and C are slight overall. Main ones are the larger stabs and the thicker dorsal fin. All other panels and rivets are identical excpet for panels on the dorsal fin and the remoavable elading edge on the stab. This of course can be dependant on which block series of the C model you are doing. The Block 25 and 32 would be the closest with the Block 30 having the main difference os the exhaust nozzle. Determine an actual tail number as I can help you a bit more.