Haven't used it on a 6 volt yet, But I use a little device called a Battery Bug. It wires straight to the battery, has an LCD display shows your voltage and percentage of charge. Very east to install. takes up little space. and you do not mess up vintage  panels.   

I have one from NAPA like Kim is talking about, The rest of the ones I use including my 6 volt one are Battery Tender name brand. You can go on ebay and find them reasonably priced. If you want more than one you will find them in lots of 2 or more and no shipping.

I use one, Switch it back and forth from the Model A to the 30U. works great. Keep them on my bikes and fork lifts and I have a couple that I switch around on customers bikes. Nothing is worst than someone coming to pick up their bike and it want start. The battery in the A is about 7 years old and still works great.

Like frankp says, #4 cylinder you take the plug out put a stiff wire through the hole and find TDC

The two wing cap was on an UN restored early 30U and still owned by the same family that purchased it new. I have seen some others, Do not know if Plymouth offered different caps. I do know there are several differences in Early 30U and later ones. If I found a cap like that for sell I would use it.   

My pump has the oil vac markings on it but like I said earlier when I connect the vacuum line to the oil pump I lose oil pressure. I attached two pictures on is before it was cleaned up and you can see the way the oil pump was plugged then the next is how I have it now. It;s not original but it works. 

30U also had a had a 2 wing cap

This doesn't answer your question, But I have my fuel vacuum attached to the intake manifold. I works fine except at idle I will get a rich mixture when the pump opens. My problem with attaching it to the oil pump is that I lose oil pressure and I am not sure if I have the correct fittings. So any information on this would be helpful.   

It's a little late. But is you had taken the shift tower off and the hand brake. The transmission would have came out with the engine. Just saves all that working under the car.

That is a great car. Like Chet says. Use fuses, A lot of my repair work on customers stuff if from electrical stuff being wire with no fuse or the fuse not being installed properly.

Here are two pics of the clamps. I havn't dusted lately

Here is a picture of my 30U before it was cleaned up. You can see the tag mounts on the bar.

What he said. Antifreeze is good for the cooling system. water from a tap has to many menials in it. 

You know this. flip the dif

I have no idea how old the belt was that was on my car when I got it but one Sunday My wife and I were out riding around and I heard a loud thump, At the time my amp gauge didn't work and we were on the open road so there was no increase in temperate so I kept going, When we got back home I raised the hood to cut off the gas and there laid the belt. The was the thump I heard. Went by NAPA the next day and got this one, 5L390W, fits great been on there for a few years now, no problem. One thing. It's green with yellow letters on it.