GMC 305 V6, The baby of the series!!!

You might want to think twice about that.
The shop manager at the dealership my dad worked at had a new truck. short & wide but fitted wih 3.07 gears (which was an option in those days).
Did fine on the freeway, but it could barely pull a load in the bed....and don't ask it to tow anything!
There was a 3.54 gear option as well. With the SM420, first gear overall reduction is literally 25:1 and it should cruise @ 50-55 mph no problem.
A friend had a '64 with the heavy duty 4-speed and a Dana 60 in the back with 4.11's. He put 33-12.50's on it and it would run about 50-55 about the same as my '65 would run at 45.

 

Something tells me this has to do with counting links, but I'll ask anyway.......What was it that you weren't doing when trying to time the pump?

 

I simply wasn't on the power stroke at TDC. There was a series of gears and idler gears that drove the camshaft and injection pump. Someone had installed a idler wrong and when the marks lined up the pump was injecting too late. This was back in 1980. It was a former Tyson Chicken hauler truck. And the title stated it was a gas engine. I suppose Bill Tyson was not paying the road use taxes?

 

Of course.
That's cool that it didn't use a chain.
The gear arrangement kinda sounds like a Detroit.

 

The gas burner V6 used a real long timing chain. I once bought a V 6 bob truck At the County Surplus auction. It had a locked up 351 V6. I tore it down and it was a almost new long block. When it was installed someone had replaced the oil pump with a 305 pump and the pump drive was rubbing the block and wore in two. and it had bearings welded to the crank. I had a 305 I had pulled from a 62 pickup. So I put rings and bearings in it. used the oil pump that was incorrect for the 351 and the heads from the 351. installed a 6 yard dump bed. And when I tried to license it with the original certificate of origin. The revenue dept wanted me to pay the sales tax on what it cost new. I refused. Still had the county emblems on the doors. So when I used it I wore a shirt that I had left from when I worked for the County Road Dept. The one time when The law stopped me I told him to take it up with the county judge. I eventually sold it to a guy that ran a small gravel washing plant. He used it off road and never needed any title.