consistant misfire out of nowhere
Yes and no.
You can do a crank-rock test. This is rocking the crank backwards and forwards,just enough to take up the slack in the chain. The valve gear will tend to keep the cam from turning.
The results are interpretive. The best result is if the there is near zero crank-rock.This is only achievable with a new chain, and even then,its only near zero. An old ready-to-jump chain might have 10* slop, or a bit more. So between 2 and 10 is subjective. A double roller chain on steel sprockets will run pretty good, and reliably nearly forever. One of those "silent" chains and nylon toothed sprockets, not so much. They often expired on teeners at well before 100,000 miles.
There are two ways to tell if the chain has jumped.
1) if you have not yet disturbed the timing, You can check the rotor to #1 tower alignment, with the #1 piston at TDC/compression. This is somewhat difficult to do, on account of the dizzy being down in a dark crowded hole. And it is somewhat interpretive, as the rotor can be quite a ways off, even in a normally running engine.
2) Split overlap. The point in the cam cycle when both the valves for a certain cylinder are open about the same amount, is called split overlap. The exhaust will be closing and very nearly so, and the intake will be just opening.This happens at the end of the exhaust stroke, and very near to TDC.Usually within about 5 degrees or less depending on the cam, the install, and chain-stretch.
So off comes the valve cover. Set the balancer to TDC/exhaust stroke. Then rock the crank back and forth while observing the rocker arms for #1 cylinder. This assumes the balancer marks are accurate, and the valves are correctly lashed. If in doubt, lash the valves to near zero and both the same. Dont forget to reset them after the tests are in.