Could be a few reasons that come to mind. I am no garage mechanic but have dabbled quite a bit with engines.
Yes it could be the HT leads, coil or distributor. I am sure there is something you can do with an amp meter attached to each lead to test them. Also check inside the distributor to make sure the contacts are not black ( normally distributors just pop off with two clips , but I am not sure how your modal fits )
Check your spark plugs.
When turning off your engine does it pink at all ( carries on running for a beat or two)? If so then there is a good chance your timing is out.
If it is something electrical then sorry it is out of my league lol