Brings back memories from high school.  A good friend in the neighborhood had a 1967 Cougar XR7 with a 289 but 4 speed.  It was originally light yellow but he got it repainted light metallic blue.  He was 16 and a year older than me and another of our friends so he would sometimes drive us to school, out cruising to the ice cream joint, etc.  Of course, his next car after a year or two was a big block '68 Camaro RS convertible.    He pointed out it was a year newer.  And that you could tell the difference between '68 and later cars because that year it was required to have front side turn signals.

Anyway, hope the purchase pans out.

Pat

https://commons.wikimedia.org/wiki/File:Hells_Angels,_Flying_Tigers_1942.jpg

Cam is  SS 310 nc
:
Anybody have specs on that old Crane solid cam

Here are a couple of threads on the old forum, on the cam.  I think one reply is from you? 

https://www.fordfe.com/is-this-an-old-crane-part-344041-t40423.html
https://www.fordfe.com/crane-ss-310-cam-questions-t59475.html

Pat

If we get to vote, I'm for doing the 4 speed swap at the same time, too.   

Bolt the bellhousing and transmission to the engine and put them all in together.

Congrats on your new car and hope you have a great time whatever way you go!

Pat

I had to buy a generic FE distributor from Autozone while on the road.  Later I went to tune it and it seemed to have only 10 degrees of advance, all in by 1900 RPM.  I think I revved it to 3000 or so with no change.  I took it apart and measured the slot width and it should have had like 30 degrees of advance at the crank, 15 at the distributor.  But it had one medium spring and one really heavy spring, so I was only seeing the advance until it hit the heavy spring.  I suppose maybe if I'd I'd kept going, I might have seen more advance in the 4000-6000 range. 

I ended up welding the slot to give 20 degrees crank advance and replaced the heavy spring with one of the light Mr. Gasket springs (925D kit).  I left the other medium spring in place.  The 20 degrees advance is all in by 3800 which is still a little high.  I should bend the pins in a little sometime and try to get it all in a bit sooner.

Pat

Since it does it while idling, can you watch it idle at night and see if you see any flashes?  Might have to drive somewhere dark depending on where you live...

Pat

The distributor springs being too weak was the first thing I thought of.  Although I did have an identical problem that turned out to be choke related.  On mine (Holley 2 barrel, part of 6v setup), the choke was almost but not 100% fully open.  Sometimes the fast idle screw would just barely catch on the lowest step of the cam, bumping the idle speed.

Pat