You are correct on the measurement of the head, TimC, it is 1.780. I was reading the caliper inverted and must have transposed the 7 and 8. I guess we can be certain that this is a .45 now, and I will treat it as you guys suggest with 5% nitro and 20% castor. This thing seems to be in very good condition, probably an 8 on a 10 scale. There is virtually no darkening on the side of the pistion, has very good compression, and the bearings are silky smooth. Probably be a good engine.