Did you install the distributor in this motor; and then install the plug wires in the cap? It sounds like the ignition timing is way too far retarded; or the plug wires are in the wrong position in the cap.
The firing order in the dstributor cap runs clockwise, and is 1-8-4-3-6-5-7-2. The cylinders are numbered from front (radiator) to back (firewall). On the driver's side; they are numbered 1-3-5-7. On the passenger side; they are numbered 2-4-6-8. Make sure the wires are located in the cap in the proper firing order. If any wires are out of order; correct the sequence. The #1 plug wire should be in the cap position which is closest to the front of the motor (in the 12 o'clock position if you were looking down on the distributor from behind the motor). If there is no wire terminal pointing exactly straight forward; you'll have to use the terminal closest to 11 o'clock. If the wires are not in the proper position; take them out of the cap, and reinstall them in the proper firing order; starting with the #1 cylinder wire.
Turn the motor until the timing mark on the lower crank pulley lines up with the degree scale on the engine; at somewhere between 0 degrees TDC and 10 degrees BTDC. With the crankshaft in that position; remove the distributor cap, and make a mark on the outside of the distributor directly below the tip or the rotor. Then put the cap back on, and see which plug wire goes into the cap at that mark. It should either be the wire for the #1 cylinder (front cylinder on the driver's side) or the #6 cylinder (third cylinder back on the passenger side). If the rotor points to anywhere else except exactly to the #1 or #6 cylinder wire (even halfway between 2 wire positions); the distributor shaft was not meshed with the camshaft gear in the proper position.
If that is the case; the distributor will have to be lifted far enough up to enable the rotor to be turned freely; and then reinstalled so that when the hold down bolt is in place, the rotor ends up pointing either directly to the #1 wire terminal, or directly to the #6 wire terminal (whichever is closer to where it now points). If the rotor already points to either the #1 or the #6 terminal; it may be that it is 1/2 turn off of where it should be. Try lifting the distributor up and moving the rotor so that it points 1/2 turn from where it was before. Bear in mind that the rotor will turn about 1/8 turn clockwise as the distributor is lowered into place and the gears mesh; so it is necessary to start with the rotor pointing about 1/8 turn counterclockwise from where you want it to end up. If the distributor does not slide all the way down into mesh; it is also sometimes necessary to remove the distributor and turn the slotted oil pump drive shaft (in the center of the distributor well) with a long screwdriver; so that the slot in the shaft lines up with the position that the blade on the end of the distributor shaft will be in when the rotor tip points to the #1 or #6 cylinder plug wire terminal. It may take several tries to get the distributor shaft meshed properly; but it must end up exactly right.