Bill,
I intend to get the Morgan Spares 5-speed kit for my 61 +4, as soon as I can spare $5,000 and two weeks of garage time.
You are right that driving your flat rad on interstates is going to be too hard on your engine. You may be aware that the Moss boxes on flat rads were "close ratio" boxes that had lower gearing than the "High ratio" Moss boxes that were fitted starting 1954.
A friend in Virginia has installed a Sierra 5-speed in his 67 +4 and he loves it. He does have some problems with the engine-to-transmission adapters, because he did not use the Morgan Spares kit, but instead modified a cheaper kit designed for a Triumph TR4. (The Morgan Spares kit is more expensive in part because it includes a royalty to the widow of the man who developed the conversion kit.) With Morgan Spares you get a kit that you know will fit and you know you can get expert advice.
Last edited by MacMog; 25/11/15 04:20 AM.
