The large Lyman handles can be easily modified to fit my blocks, and NEI and LBT blocks, too.   The Lyman is made from a casting and only part of the prong (is that what it is called?) is machined to fit in the blocks.   Just make the machined part of the prong about 1/4" longer by grinding or filling or milling off more of the unfinished cast portion, as shown in the picture.   It took me about 5 minutes to modify these handles on a bench grinder, pausing a couple of times to check the fit.   Now they will fit Mountain Mold / NEI / LBT / RCBS molds and of course, they still work on Lyman blocks.