Red: Actually, the (TKS-)MCC120 (the TKS prefix is only for the special, non-halfinch-mount but second generation proprietary ULM mount variant) already is a pretty good cartridge - in fact it's a slightly modified, but unfortunately not needle compatible variant of the Audio Technica AT30HE high output moving coil cartridge with user-replaceable needle. And just like the AT30HE can be converted to low output, if one puts on the needle ATN30E or the better ATN31E instead, the MCC120 also turns into a low output moving coil, if one puts on a DN110 instead of the DN120 (which may both actually rather be on ATN31E quality level, as Dual specified a smaller minor radius for these than AT did for the ATN30E/30HE). New old stock original DN110s and DN120s are not quite easy to dig up anymore, though - but for example Pickupnaald.nl still seems to offer both variants for not quite 140/150 Euro. And usually the new old stock original needles still are in very good shape.
Other 2nd generation ULM mount cartridges options with reasonably high quality for a 741Q would have been the Ortofon-made TKS60E (though only with the earlier, nude variant of the DN160E needle - the later exemplars were bonded only and thus not really better than the cheaper DN155E anymore...) or the Shure-made TKS380E/390E. The latter were close relatives of the Shure ML120HE/140HE and Ultra 300/400 families, the needles of which one can still use to upgrade the TKS380E/390E to pretty high quality level. However, new old stock originals of these needles are also already pretty rare and not quite cheap anymore - not to mention that you'd still need to dig up the matching Dual bodies. So keeping the TKS-MCC120 would seem the most sensible approach in your case.
Well, and then one could convert the 741Q to halfinch-mount, either with the matching, rather rare and expensive and for my taste also rather ugly looking halfinch-mount adaptor kit, or with some modding work and the halfinch-mount 3rd gen. ULM headshell of the 505-3. Personally I'd rather avoid either option, though - 'cause just as the ugly adaptor plate the darker headshell would also spoil the visual appearance to a certain degree. So that's another not so bad reason to stick with the TKS-MCC120 - at least as long as one can still dig up original replacement needles for it.
Greetings from Munich!
Manfred / lini
P.S.: I can understand that you still like your 630Q, 'cause that wasn't bad at all - although it surely isn't as sought after as many of the older, more classic Dual models, which most Dual fans seem to prefer. But if one isn't generally opposed to plastic-encased tables, there's not much that would speak against it. Its 3rd gen. ULM arm version still is pretty good, and the direct-drive and its quartz-referenced motor control deliver pretty good performance, too. Not so great in the long run: the otherwise nice, numerical speed display tends to fail sooner or later - which is why I'd prefer the otherwise identical 620Q without speed display and pitch control.