What is it?

I purchased a v8 for my series 2 (1958) End of last year . I was informed by the seller it was an 3.5 v8 out of a car from around 1976 ?. I've just stripped it down and the numbers I've found don't seem right . On the head numbers are 36D04692A . And on the block it's 9E691 wyf HTC1800. can anyone tell me which block and year from these numbers please . (I've done a little research and I think it's a 4lt? But no idea what year and what it came from.) Many thanks,

36D (below n/s head) is engine no. 3.9 disco rrc auto 1988 onwards cr 9.35:1