340 recommendations

This has good potential; cngrats if is a good engine. Even then, you have some good parts.

1. Fresh oil and filter
2. Remove plugs and spray some WD40 into the cylinders and turn sloooooowly by hand. Don't force it at any point. There is likely to be some rust in at least one cylinder; how well it will work out is anyone's guess; at worst, it can break a ring and crew up the cylinder walls. (see below)
3. Drain and change the coolant. Those AL heads will be effected adversely by coolant with the additives broken down over time. And if is just very weak anti-freeze mix in there, then the head cooling passages may have a lot of milky crud in them which is corroded aluminum.
4. New plugs, rotor, cap for sure. Clean up the ignition system wiring mess! Test plug wires for consistent resistance
5. Pull carb and dissassemble and clean; its easy to have gummed fuel in there.
6. Pull and drain tank and clean and blow out all fuel lines and change filters. You gotta get ALL of that crappy old fuel outta there! Old fuel can detontate and put holes in pistons, and also can get on valve stems and jam them open and then you have bent valves and pushrods and broken rockers and all the rest.

For #2 above: Personally, I would pull the heads to examine the cylinder walls for rust, get any rust out before it can chew up a cylinder wall or ring. If the block has indeed been bored .060" over, then it is at it's very last bore (unless you are really lucky on that particular block), and 340 blocks run in the $400 range and up for a decent one. Damage to a bore now will probably end that block's life.

Do the same for the intake, head ports, valves and seats and see inside of the head cooling passages. Your have some valuable parts; those heads cost over $1500 new by themselves. In untouched form, those heads flow WAAAY beyond factory heads. Why risk damaging them?

If you pull the heads, take some pix so we can see the pistons. Someone here may be able to ID them for you and then you will know some important info about the engine.