D3VE's are 1973 to 1974 heads, 91.4 cc's with 2.08"/1.66" valves. Apparently, someone has changed the heads along the way, probably to lower the compression ratio so that the motor would run on pump gas and also to get induction hardened valve seats. Of course, the whole motor may be later than '69. The '69 heads had 75.8 cc chambers.

The most effective change you can make to the motor is to replace the timing set with sprockets and chain for a '68 to '71 429. The '72 and up motors had the cam retarded with a different keyway location on the crank gear for emissions purposes and they wouldn't make any power.