Some additional semi-random comments on T&G planes and combination planes:

I should point out that the vintage #48s (and their cousins from Union etc) were designed to center the groove/tongue on 7/8″ stock. They will however work just fine down to nearly 5/8″ stock but without centering the elements. The #49 was designed to center on 1/2″ I believe.

The new incarnation of the #48 from LN is designed to center on 3/4″ stock but will work fine down to nearly 1/2″ stock, with the commensurate shift in the planed element of course. While it is pricey, I’ve had ample opportunity to use them and they are NICE. If you expected to be making solid wood backs for cabinets for the next 30 years, you should seriously buy one. If on the other hand, you don’t have the money to spend, keep looking for the vintage metal or wooden stock planes.

FYI, with wooden stock T&G planes, sometimes they are a matched set, other times not. Harlequin sets can be made to match with some care. And like their metal counterparts, they were often designed to center on a specific stock width.

If having perfectly centered tongue and grove joints is your thing, then the combination planes are the way to go.