So shall I paraphrase your answer is 4-1/8 bore, and probably something between Std and 0.040 over? Anyway at this point your not commiting to anything other than an interest.

I wouldn't dare hazard a guess on price, but I'd suspect that if the demand was comparable, they wouldn't be much different that the autothermic strut pistons Dan already has made for the other Packard engines, but perhaps a bit more since I suspect the larger bore sizes will mean they contain more material?

Yes, I hope we hear from them as well. I'll let this thread run its course for a while yet and then pass a summary of it along to Dan Kanter.

Can't be a left-over 359, that engine didn't come out until 1954 and would be painted bronze. And as I said earlier it can't be a left-over 356 because except for the marine engines, that was discontinued at the end of the 23rd series, and besides although I suppose someone might be able to make a 356 fit the 24th series chassis, there is so much that is different like motor mounts, water pump, etc. that's it's somewhat unlikely. My best guess is that although the green paint on your engine may appear original, it probably isn't and it's just an ageing repaint. The "J" prefix is correct for a 24th series (1951) engine.

Good points, and well said Brian.

Of course we have to remember that these claims were made by Packard themselves, and there is often some small fact that can bring some of them into debate. I'm hoping this thread doesn't lead to the ugly, virulent spatting and sniping that occurred when this list was posted over on AACA some years back. Regardless of some doubt that might be cast on a few of the items, Packard, despite making very conservative cars, was a innovator throughout most of their history.

Perhaps I can add a bit. I've seen many Packards in factory RHD, including quite a few Full Classics. While I don't know of any "kits" to convert to RHD, Packard made RHD cars (though I'm not sure about the TWelves) from scratch both in Detroit and in Canada, the latter especially for export to South Africa, Sweden, and of course England and Australia. I believe the Canadian plant opened about 1931 or 32 and closed just before WW II, and as late as 1954 the parts manual shows the various parts for the RHD cars which were available only in certain chassis (only the Clipper DeLuxe, Special and Super for 1954)and the Service Counselor shows the finished cars so available. So while perhaps never many in number, Packard had a very long history of manufacturing RHD cars. After 1954, Packard relied on their London Distributor, Leonard Williams, to do the conversions. You'll find a test report on a 1955 RHD Clipper so converted somewhere on this website, and you'll also find a photo of a 1934 Eight or Super Eight RHD chassis under restoration. I believe there is an original photo of a Classic-Era RHD chassis on the Michigan University archive site. So an Twelve in RHD wouldn't suprise me in the least. What I'd like to see if the Patent Plate (VN plate) picture.

Sorry folks, I made a mistake above. Yes the gray color started with 1948, though there are some unquestionably original 1948 cars with green engines, though they are all (to my knowledge)Custom 8s with 356 engines. And Packard couldn't have been using green on the 356 into 1951 because the 356 engine was discontinued with the 23rd series except for the marine engine series, in which it was painted gray.

Not sure about 1951 though the answer can be found easily enough in the parts book, but the 1954 thru 1956 Senior cars with Ultramatic used a different ball and trunnion (front) joint that the junior cars. If you have a senior and need the housing, buy it at any price as they have been nearly impossible to find for many years, to the point where people are spray-metallizing the old ones and remaching the internals. The rebuild kits are still reasonably plentiful and may interchange with Chrysler, I don't know; they contain the balls and caps, needle bearings, pin and boot. I also don't know if the Chrysler ball and trunnion joint interchanges with the junior or senior cars, but it would be a useful answer for someone to determine and post here.

Radial tires have a lot of advantages, though steering more easily than bias ply when the car is at rest is not one of them.

Your engine should be gray, no question. There is a bit of controversy over whether the change from green to gray occured during the 23rd series (1950) or at the beginning of the 24th series, but no question that all the 51 motors were gray, as were all the engines thru 1954 except the 1954 senior (359) engine which was bronze. Perhaps someone in the past repainted your engine. There are differences with motor mounts, waterpump etc. starting with 1951 so I coubt your motor is an earlier transplant, though anything is possible. Check the motor number if in doubt.