Any '55 will happily run on regular gas with nary a knock.

That spring bolt has a large head on one side that fits inside the large hole. It has a moderate sized body that fits to the spring bushing. That dia. is turned further down to the thread size that fits through the small hole in the frame and is then retained by a nut.

At the introduction of Ultramatic all crankshafts were bored to a larger pilot bearing diameter. There is not a scintilla of difficulty changing between Ultra and manual due to that fact. All the man needs is the dimensions of the large pilot bearing that was used mid 49-54. I am 8000 miles from home so can not measure one for him.

If you replace all of your brake tubing and install new hoses and cylinders, the risk of instantaneous brake failure is small to the point of nearly vanishing. That is unless you plan to run the car in the salt.

In 52 years of screwing around with old cars the only instantaneous failures I have seen were due to corroded brake lines. Sure I have seen diminished performance for a host of reasons--all due to lack of maintenance and wishful thinking, but instantaneous failure was always from corroded lines.

I have seen poorly engineered dual cylinder retrofits where the pedal stroke was not sufficient to operate the second half of the dual cylinder if one half failed. The very picture of a fool's paradise.

Almost certain that the overdrive locking sleeve is hanging up or the little tab on the reverse shift fork that is supposed to push the sleeve to the rear is worn. When it acts up, try pulling your lockout knob out all the way.

I'd suggest removing the entire dash from the car, rewiring it and then putting it back. That way you can deal with a thousand other nagging details, for example the heater bowden cables, lubing the speedo etc etc from the comfort of your workbench. That would be a great time to rebuild the heater valve too.

I also strongly recommend changing the car over to column shift and donating the pushbutton unit to the Museum of Needless Complexity, for display in their Painful Unreliabilty Gallery. Just my opinion. And experience.

Congratulations. Very nicely done. What is your sewing machine?

Please note that your car seems to have an adapter fitted onto the manifold that allowed the use of the "tractor" carburetor. You will want to measure the throat and bolt pattern of the manifold and not the adapter.

Undo the shift linkage from the lever in the engine compartment. Loosen the clamp that holds the column to the steering gear. Remove your floor plate and unscrew the rubber collar where it passes through the firewall. Remove the bottom clamp at the edge of the dashboard. Yank. And turn.

Then you can deal with the rusty bolt that retains the upper half of the column clamp to the dash.

The chart is confusing. The first column describes which engine the head is FROM. The next columns give the compression ratio that results if that head is installed on the other engines.