Nailhead question for the guru's

I have a buick nailhead motor that I need some help identifying. Hoping some nailhead guru's can come up with some info for me. I was told I have a 401 block with 425 heads. These are the numbers:

BLOCK:
LT 351 V581 5H213261
(the second to the last number has a line above the digit)

HEADS:
1374603

If anyone can tell me some history on this motor I'd be very grateful.

Thanks -Jon

 

The block is a '65 401. That's the LT code.

The head castings are 64-66 and are the same for 401 or 425

 

aren't the heads between the two the exact same thing?

edit: nevermind, answered above

 

Thanks for the info guys. The seller was straight up with me, cool.

 

This might help ya............... http://www.buicks.net/shop/reference/nailhead_casting_numbers.html