Hi Bud, and thanks. The numbers are definitely Hepolite from the period, I worked as a manager for many years in a motor parts company who specialised in engine parts, and were a part of AE, who also owned Hepolite, so I'm familiar with the numbering system. The only catalogues I have are for rings, and carry cross references to the pistons that they fit, they list Gilfords with 6 cylinders at 3-7/8", but the numbers don't tally. There are are usually a few catalogues for sale on ebay, but they're silly money, I've identified all the other pistons I've got, it's just the Gilford ones , so not worth me investing!
They may end up in the scrap bin yet, a shame if somebody can make use of them, I'll sit on them a bit longer, I'd put them on ebay, but it's a bit difficult when I know so little about them.
Bernard