If you have a Vintage McIntosh preamp you have built in MM phono input with MM RIAA phono eq (perhaps two phono inputs, front selectable). Also many other nice features.
For a low output MC cartridge (like yours 0.6mv output), all you need is to boost the signal (pre-pre boost) up to the level of a MM cartridge, then feed it into your preamps MM phono input.
SUT (step up transformers) do just that. They are passive, they do not change the sound, thus you keep the sound of your MM phono stage, in the case of tube McIntosh Preamp is terrific IMO.
You always want a ’PASS’ setting, so you can simply pass an MM or High Output MC signal thru (bypassing the SUT's internal transformer's windings).
The impedance shown to the phono input is related to the amount of signal boost and the cartridge’s coil impedance. Complicated, but worth learning or asking for advice before buying.
I chose a Vintage Fidelity Research FRT-4 SUT with 4 optional impedance choices (and 3 selectable inputs, most do not need that).
this one has silver faceplate, and little nicks/corrosion
https://www.ebay.com/itm/394503791725?mkevt=1&mkcid=1&mkrid=711-53200-19255-0&campid=5338381866&toolid=10001&customid=a908a282-dc4e-11ed-b84a-326433663330
usually they are gold tone faceplates (this faceplate more dings ....
https://www.ebay.com/itm/155407979749?mkevt=1&mkcid=1&mkrid=711-53200-19255-0&campid=5338381866&toolid=10001&customid=e4c7f11a-dc4e-11ed-b668-326433663330
this entre 100 also has 3 optional loads, (and 3 inputs)
https://www.ebay.com/itm/134511637279?mkevt=1&mkcid=1&mkrid=711-53200-19255-0&campid=5338381866&toolid=10001&customid=36ab9536-dc4f-11ed-8786-326433663330
there are other units with external or internal dip switches, removable resistors, etc that provide even more impedance/signal boost flexibility
btw, your McIntosh preamp probably has trim pots to balance the incoming volume of a few sources, so you don't have to change the preamp's main volume control when changing sources.