87 Diplomat is the same core package with 302 heads on a 318, but with barely 8:1 compression, choked down exhaust, and a lot more weight than my little 65 a-body. Diplomat has lock-up, but my Valiant has OD so that should equal out. I don't think 25 mpg is out of the question for my combo. I agree with a lot of the other guys that weight makes a big difference on avg mpg especially in city driving.