The last year was 1981, and the 534 was offered in C/CT-900's and Louisville 900's. VERY few were built after 1977 or so, and most of the later ones ended up in fire apparatus or were industrial 'crate' engines. I don't have the H.P. and torque figures handy, but at the end the 534 was in the ballpark with the Lima 429. That was a big reason why it was dropped in 1981.