Vince,
Glad to hear that you finally have the tailstock fixed.
First, keep the 2MT dead center. It fits the headstock spindle taper. There aren't a lot of uses for it but one is measuring runout or straightness of a round bar, or of any round part that can be held between centers (small crankshafts, for example). Another use, which requires a face plate, lathe dog and piece of steel 8 or 10" long, is to make a test bar (and later to mount the test bar for use) to use to set the tailstock offset or backset and check its height.
The 618 and 6" Mk2 tailstock ram has a #1 Morse taper bore. Right now there are more than a dozen #1 Morse taper dead centers on eBay, most around $10 and most imports. If you decide to buy an import instead of US, I can recommend one made by CTC Tools in Hong Kong. I haven't actually bought a dead center from them but have bought full sets of 2MT and 3MT collets and all are excellent. There are a lot of #1 Morse taper live centers listed as well. Again most import.
Robert D.