[Mark IV]

Exhaust mainifold is 1963-64 thunderbird LH (uses a donut to seal to H pipe, 61-62 used a flat gasket)

Block casting number and date indicate a 61 block, the 65 engineering number, 64 casting date intake is probably just a mish mash configuration. A little bit of creative boneyarding probably created the combination.

Does the block have an alternator mounting boss cast into the RH front side? Only some very late 62 390s going into alternator try out on 1962 late build T Birds had that, otherwise the alternator boss did not appear until 1963 production and a C3 casting code.