I need some help with headrests and seatbelts

May 1, 2010 | By Richard Prince


I would like to ask two questions relating to vintage vehicle safety regarding my old car (a 1955 Chevy four-door sedan). First, what would be an updated or upgraded bench seat I could use that has high-back headrests which would fit without much modification?

Second, I would like to install seatbelts with shoulder harnesses. What could be used and how could the shoulder harness be anchored on the post?

Also, when I bought this car, the engine had already been upgraded with a small block Chevrolet V-8 engine. I sure could use some help with the identification of this engine. The suffix code has been milled off and there are no

letters or numbers where they should be. The casting number on the block is 3970010 and close to this number is either 4CM or 4GM. (I’m not sure about the letters, CM or GM.) The head casting number is 376450. The intake manifold casting number is 346250. Is this engine a 302, 305, 327 or 350 displacement? Many thanks and it will be appreciated if you can help the old guy.


I don’t know offhand what headrestequipped bench seat would fit easily into your 1955 Chevy but I have two suggestions. The first is to measure the seat that’s in there and then go salvage yard hunting for something that’s very close.

The second, and the one I’d do, is to add headrests to your original bench seat. I have done this numerous times and it’s not particularly complicated.

You can salvage all of the needed parts out of many different seats that came with headrests. Weld the necessary brackets and supports to your original seat frame and, if needed, recover the headrests and/or seat to get them to match and look good.

Installing seatbelts and shoulder harnesses is not difficult but it obviously is important to do it well. In a nutshell, you must anchor the belts and harnesses at the proper location and angle relative to the passengers, and in a way that is sufficiently secure. If you are not comfortable doing this yourself then pay a qualified professional to do it. An experienced and knowledgeable race car fabricator can help you with this.

I can’t tell you the displacement of your engine based on the numbers you provided. “010” blocks were used with various OEM displacements but more of them were 350 cid than anything else so just based on the laws of probability your engine is most likely a 350. However, even if it started life as a 350 the displacement could have been changed somewhere along the line by virtue of a crankshaft change and/or cylinder boring. The only way to know the displacement for sure is to measure it.