1965 gto engine information/ correct motor?

Hi I recently purchased a 1965 Gto and I was trying to determine if it has the correct motor in it the numbers on the block are 25k 552810 6 and the numbers on the heads are 877334 the vehicles vin is 237375p272152. One number id page I found said this was a 1964 Pontiac motor and I was not sure if any 65 cars had a 64 motor in them. Please respond with any info

Pontiac Motors Cast Plant, Plant #6 had it change-over most of the time in July.
The 1965 model year cast date started in July or August 1964 = H-(00)-4 or H-22-4 = Aug. 22, 64. This date would be at the rear of your engine near to the disributor.

John

If your engine block is a 1964 block,the 25K coded engine came from the factory in the big cars like a catalina,bonneville,star chief,or grand prix.The heads you have are probably the correct heads for your 25K block,if you scrape some more gunk,they are probably a 9773345.That 25K block is a 303 horespower rated 389 from the factory with a 10.5 copression ratio.The 4 different engine codes you should have had in a factory 65 gto are YS,YR,WT,WS....Kevin