Will these 18x9 wheels fit my 64 cuda??

What brake kit are you planning on using? I believe either the Wilwood and/or Dr Diff kits pull the hub surface out a bit. Also what size tire do you plan on running? I'm not sure but doesn't a '63-66 car have smaller wheel tubs than the '67+? I'm not really sure as I haven't dealt with an early A. You'll most likely need tubular control arms. I'd recommend a 245/45/40 on all 4 corners as a start if you don't want to do any cutting or trimming.

For my '68 Dart, with a +30 mm Mustang wheel (about a 10" wide tire and 26" tall) I would hit the frame rails in the rear at full lock and full droop. When will you ever be in that situation, probably never, but I just through in a +5mm spacer on my new wheels to have an effective offset of +27mm just in case. I'm running a 255/40/18 on all 4 corners. There seems to be a decent amount of room in the front. For the rear, I had to get the offset PERFECT! I still don't know if they'll rub as I haven't driven it but we'll see.