Tom,
Well, I tried the rubber seals twice in my 262, and have gone back to the graphite rope seal. I think that maybe the size tolerance applied to the factory Hudson parts doesn't always match up with the Chrysler parts (rubber seal based on the 318).

Based on my experience, it wouldn't be advised, however, I do know some people that have had success with them. To me, it doesn't seem to be worth the risk of whether it will work for you or not.

My .02,
Doug

Tom,
Used the robber seal and it leaked like a sieve. Many replied when I inquired and were very unhappy with the rubber seal. My advice would be to use the rope seal. My mistake in using it cost me another $550.00. Rope seal was installed and there have been no problems
John

My experience is similar. Tried two of the neoprene seals and they failed. This was on the '48-54 232-262-308 blocks. I also installed the neoprene seal on a '51 Hornet before the other two failed on a '51 commodore Six. So far we have ran and driven the '51 Hornet with this neoprene seal with no visible oil leak. On the '51 Commodore Six, I finally threw in the towel and put in the Best Gasket Graph-Tite rope seal with success, and this was done by taking the engine out and putting on a stand with crank out, so I could properly clean the upper groove and pack the rope seal into it well. I have l have also installed the original Brummer neoprene seals into the '55- 56 308 blocks with no problems, but then these blocks were specifically machined for these Brummer seals.
The issue with using the Chrysler 318 retro-fit rubber seals in the 1948 thru 1954 232-262-308 blocks is due to the wide variance in the tolerances during the machining of the seal groves in these older blocks and rear main bearing caps. The thick rope seal is packed tightly in the groove and can compensate for a wider tolerance in the groove width and depth, along with a smaller crank seal journal diameter. The stiffer metal backed rubber lip seals need closer machining tolerances for the grooves and crank seal journal diameter to be able seal effectively.

F.Y.I.
In fairness regarding rear Seals, Ive installed several Mop;ar 318 Neoprene Seals without problem and two of them are in race motors; Perhaps im just lucky or its because after cutting the ears I put Utra Black RTV in the corners without even rotating the gaps away from the parting edges.The only Seal Ive used is Fel Pro #BS 40245 and will use another in next motor. Additionally, I put Ultra Black in the 'grooves' while packing the string into the Cap..

We have installed many, many rear main seals. We have found the graphite rope seals work very well. Most of the time, the sealing surface is pitted from where the seal had sat for years. The original, cotton rope seal worked very well, but after many years, the graphite is gone, leaving only the cotton with very little graphite in it. This allows moisture to absorb into the cotton and subsequently rust and cause pitting on the rear crank sealing surface. The carbon graphite high performance BEST seal seems to fill the imperfections, and stops the oil from leaking acrossed the sealing surface. Make sure you also follow the side sealing instructions in the package. Installing this seal requires a rear rope seal installation tool. You can see this tool in action on our website.www.wildrickrestoration.com It also works best if someone rolls the engine over in the same direction you are trying to pull the seal in. Make sure the rear shelf of the back of the block where the rear main cap bolts is clean of any and all oil and old sealers. Make sure to Re-torque the rear main cap to specs. Again, follow the directions in the package. Hope this helps