I have a 68 Conv with 14 drum Rally II's. I found a couple of options for front disc conversions but I needed to get new 14"s or 15"s.
Note there are 2 type of 14" Rally II's rims. Drums rims and Disc rims (Discs are from 67 and have JA Code). Most of the 14" conversion kits will ONLY work with the JA / DISC 14" Rally's. So be careful. https://firstgenfirebird.org/f-a-q/rally-ii-wheel-codes/
I went with the Auto City Classic kit (not installed yet) because it was basically a 69 f-body disc factory setup with Disc spindles (versus mounting on drum spindles). And I found a nice set of 15" Rally IIs to use with them, but the 14" Rally II JAs 'should' work.
Also, AutoCity Classic said they had a 'not on the website' conversation kit with a smaller rotor that would work with 14" drum Rally II's. Of course it was more than the others, if you have drum 14"s and want to keep them, you might want to call and ask.
There were also alot of posts that I found that people with 14" Rallys (drum rims) that would grind off some of the caliper material for clearance and it would work. But I didn't want to go that route.
Good Luck. I looked for 8 months on this topic for my Bird's second resto/refresh currently underway.
Last edited by Frank - 68 Firebird; 12/31/2110:57 PM.