Pull the distributor cap... is the rotor turning? Even with a sloppy chain, it should start. The chain is pulled tight on one side during cranking. As long as you have ballpark timing, it should fire and run the pump. This was a running engine, so there's no reason to think it shouldn't still run.
But, do this: pull the #1 spark plug, then roll the engine over with the starter using a "bump switch" while holding your thumb over the spark-plug hole. When you start to feel pressure on your thumb from the cylinder (I don't care how tired it is, you'll feel it unless you're missing a piston

), quit cranking before the timing mark aligns with the tab. Manually turn the crank with a large ratchet,
clockwise only (to maintain tension on the chain), to align the timing mark with 0° on the tab. Reinstall the spark plug, then check your rotor position in the distributor. Rearrange wires if necessary, obviously maintaining the firing order, so that the rotor is pointing exactly at the #1 spark plug wire's terminal. Yes, you'll have to twist the distributor a little bit, and don't forget to tighten it when you've got it aligned. It
WILL fire the #1 spark plug at the correct time during cranking. Once it's running, set your timing as close as you can to factory spec with a timing light, or use the Big Fat Friend method for a little better performance. With a sloppy chain, though, it's still going to run a little funky.
For the record, I understand budgetary constraints and all that, but RockAuto sells a Cloyes C3028 dual-row roller timing set for this thing for $27.79 + shipping. The less-durable silent type is only $16.25, and a timing-cover gasket set is around $11 (Victor JV806). Either timing set is a drop-in; there's nothing special about the roller unit that requires different parts. To me, that's cheap peace of mind as well as accurate timing.