Looking in my service manuals and another source I have, the 383 CR has varied.
62-65. 10.0 closed ch
66-67. 10.0 and 9.2 closed ch
68. 10.1 and 9.2 open ch
69. 10.0 and 9.2
70. 9.5 and 8.7
71. 8.5

I assume all of these CR changes were made by pistons changes. As far as I know, mopar only used .023 shim steel gaskets from the factory. I have three 383s at the shop. One bone stock oem 69 non hp that’s too nasty to turn over and check. I’m sure it’s a pass car 9.2 CR. One 71 hp with oem pistons and one 70 with aftermarket .040 cast pistons of unknown CR. Both of these later 383 have had non factory cams installed at one time because both of them have valve marks on the pistons from hitting valves. So that is a major concern for sure on these 383 pistons with no valve reliefs. I will have a cam with less than 230 degree of duration @.050 because I need my power brakes to work. I may have to go even less. At least his first motor did not have that problem with KBs. He had big cam with 241@.050 but the KBs have hugh valve reliefs. My other issue is all the cost of rebuilding the 452 is fasting approaching new stealth head price. Cleaning, mag testing, good three angle VJ is $400. $100 for cutting cutting for better seal and seals. Then new springs and setup pressures and were getting close to new stealths. All the cheap crappy machine shops have vanished from poor work work like we got on these heads. These heads he has at least have new hardened ex seats and new valves but they appear milled some and still have 92 cc chambers. I’m going to measure some more heads I have and make sure it’s not my measurements. I’m going to order a new burette.