FWIW, There are not too many OEM ring makers left. Quite a few of the old names have been acquired by the "Mega/Global" companies and with consolidation and such, a lot of the old names have disappeared. Sometimes they are used for a particular style of application and not as a general "Branding" of appliations. It is getting harder to find ring packages for our "small" bored engines.
My last set of Deves was a repackaged mix of Hastings 4 piece oil and AE/Federal Mogul compression. If one knows what markings to look for, the OEM can usually be deduced.
Double check the clearance in the ring land. New spec is usually in the 0.0015" to 0.002 range. Worn out is 0.004". Bigger numbers for larger bores. Small numbers for smaller bores. Detonation is a big culprit in the wearing out of the top ring land. More common than most people think, expecially in race engines.
Aren't STD TR6 pistons about +.040 MG1500 size? Maybe that would be workable? I've got some odd ball TR/MG 1500 engine bits and pieces. I'll look tonight and see if I have anything usuable.
Not doing too much 1500 work right now, so would be willing to get rid of what I might have.
Mike