Meter, definitely. Remove the old points, install the new ones, replace the cap, connect the dwell meter and remove the coil wire from the cap. Using the appropriate allen wrench or point tool to reach through the cap window, have an accomplice crank the engine: adjust the points to 30 degrees of dwell and you're done. Replace the coil wire and fire the engine. Sure is a lot easier on your back, and your eyes than trying to set point gaps with the distributor in place. Buy a cheap meter, or borrow from a willing neighbor if you can find one ! Also, make sure the wire from the distributor is connected to the negative coil terminal, not reversed.
If you think a single set of points are fun to set, try an old Mallory dual point YL-482 like I ran for years. You can do the same thing with them as you do a window type distributor cap, only you have to set both sets of points without the benefit of a window cap.
Regards - good luck and let us know how you do.