jorb: I tried everything I can think of to examine this left, rear block area just above the pan line and so far cannot see any numbers. That said, it is, indeed, very hard to see. My camera wouldn't do much as there are vacuum lines in the way of getting it in there. The other idea of pulling the head and measuring the bore is a great idea, but at my age and bad back, that's a tough way to go at it. I think this has been a very helpful thread so far, and I hope it assists others as it has done for me. This coming weekend I'll be tied up with other things for several days, so cannot pursue it until next month. Dang. Wish I could confirm block as a 261. Maybe someone else will chime in with more insight as to the 55 number in the serial number. Still hoping.... Dennis
