['ol Pinion head]

No basement , but have a wall of rally II's... it was just easiest to measure some from the top of the stacks. Measured several JA's & then a few JT's & KU's. Used a combination square to carefully depth measure them all. HN's will measure the same as JT's & KU's (have measured them before). I have some HN's but they are towards the bottom of my stacks.

The JA's & JL's measured 4 3/8"" from the mtg flange to the very back edge of the rim. I used a combination square to carefully depth measure them all.

The JT's & KU's measured 4 1/4" from the mtg flange to the very back of the rim.

Only 1/8" difference. Tires mounted on JA's & JL's when used on the common single piece rotors will track slightly inboard. The change from JL to JT was due to the change in style of rotors. The early "2 piece" style rotor used the bolt on hub. During '70 production, Pontiac wasn't alone in changing 14" wheel codes on their '70 A-bodys, Chevy changed rotor styles, as well, & went from YA's to AO's on the 14x7 Super Stock ! wheels used on '70 chevelle SS's, SS Novas & a few Elco's.

1stGenFB, you could convert to '69 style front disc changeover & get by running all 4 rallyII's that you have, just run the JC on the rear of the car. Could always pick up another later 14x6 or do some trading.