I have a 402 I have been able to decode some of it block # 3969845 P date code 04-70 front block code T0908TKB I have found it to be built in the Tonawanda plant Sept 8th and was used in a 1971 truck Head code is 3933148 1969 open chamber 122.1cc oval port my question is everything I have found says in 1970 the compression was 10.25:1 and in 1971 it dropped to 8:1 compression so do I have a 10.25:1 being the engine was built Sept 70 or is it a 8:1 compression being it was put in a 1971 truck how do i find out what I have thanks for the help