DSS2 is just a part number for the rear casting.
Correct model is No. 700. It was Delta's first real full-sized machine tool, made from 1931 to 1938, although it was superseded by the model 1200 scroll saw in 1934.
The manual link jakemac posted is the correct one for your saw.
1/4 HP motor will work; 1/3 HP would be better. Use pulleys to give you a speed range (at the gearbox) of 600 to 1725 RPM. Slower end of the range for hard woods or thick sections, higher for soft woods or thin sections.
SAE 20 non-detergent oil for the gearbox.
Blades are standard 5" scroll saw blades.
Fixed up with a proper motor and with the reciprocating parts and blade guides in good condition and adjusted properly, that saw will outperform any currently-made scroll saw of any make.