86 E150 starts intermittently; sometimes dies

I wasn't exactly sure which forum to put this in, but here is the problem:

I have an 86 E150 5.0L v8 conversion van. It had been sitting in my garage for 3 years before just a few weeks ago when I decided to get it up and running again.

I put in new transmission fluid, changed the oil/filter and air filter. For the most part it will start up quickly and run very smoothly.

What happens is that maybe 1 in 4 times it will not turn over when I turn the key. I'll have to wait 3 or 4 minutes and then, crank the key in the ignition while applying much force as far as the key will go to get it to turn over. It usually starts with no problem once it turns over. Could this be a sign that I need a new ignition switch?

The other problem is that occasionally when I am downshifting to make a turn - specifically, a right-hand turn - the engine will die. If I slow down almost to a stop before making the turn, the engine will stay running. Any amount of excess speed causes it to die (occasionally). I have Not checked the engine timing yet.

Lastly, I noticed while on the freeway that if I drove at a speed of 45 or above while the road curved to the right, the engine would sputter a bit occasionally. Once the road straightened out, the engine ran smoothly again.

I'm planning on ordering and installing a new fuel filter. The vehicle has a canister filter and also an in-line filter. Which ought I to replace, if not both?

Thank you for your help!

Ford had a recall on these year Ford's for the ignition switch. I would change it if original equipment. Look at the screws holding it on a replacement will have tamper proof torx screws or normal bolts if they didn't have a tool. The others use channel locks.
I would change both filters.