Once again this is what I started with, a 1949 Mercury 8CM Flathead. It is a 255 cubic inch about 114 horse power from the factory. We bought an old farm truck and parted it out and I kept the engine.
I tore it down to where the cam and rotating assembly were still in the block and started cleaning. 2 days of cleaning later it looked like the picture below, with some paint of course. The water jackets are notorious for building up rust resulting in over heating, so I cut up coat hangers and put them in an electric drill. I then would spin the hangers while pushing them in and out of the water jackets to loosen any scale that was built up. It helped to have the engine on a stand so I could spin it upside down. Then I would tap the block with a rubber hammer and pounds of junk would fall out.
I installed a pcv valve in the valley of the block to help with ring seal when the engine is running.
The engine probably should have been honed and re-ringed but if it isn't stuck it will probably run, so I took a chance and started putting it back together.
I picked up an older Edelbrock Super Dual Intake Manifold to run two Holley 94 carburetors.
These engines run two water pumps so I found the truck style through Napa online. I already had my motor mounts built on the frame so I wanted to stick with what I had. I got exhaust manifolds from a 1934 Ford Flathead because they work as a dual exhaust where the merc came with single exhaust.
I switched the block over to head studs instead of bolts because they seal better and are less likely to snap off. Just make sure yoou get the correct year because they are different lengths. I found a deal on the Hamb website and found out they were for a earlier year, they still work but the bottom row has a lot of thread showing.
I picked up some chrome wire looms and a spark plug wire kit from Speedway. This was my first time making spark plug wires and it was actually pretty easy, getting them to slide through the looms was the hard part.