I have a '66 Skylark Convertible with a 350 engine. The engine needs rebuilt (2 spun bearings)and is now fully disassembled. I have a receipt (from the owner that swapped the engine) listing it as a '73 Buick 350. However, the only marking on the block is 73 and the only marking on the heads is 74. The engine was orginally a 4-bbl, but the original carb has been replaced with a Holly. My question is that I need to replace parts in this engine (crank shaft for one), and I don't really know what year everything is from. How do I find out if some parts were the same for several years or if they were different? Also, how do I know what year this engine came from?

John, the starting point is the block. Buick stamped an engine serial number on the block to tie that exact engine to the car it went in. Also there is a production code number stamped into the block to indicate year, CID, build date, and possibly a few more application details.

On the 73 and 74 units, the engine serial number will be stamped on the front of the block below the right side cylinder head. It will be in the form 43H100001, where 4= Buick div. of GM, 3= 1973 model, H= manufacturing plant, Flint, Mich. (home plant), 100001= serial number of the first car (and its engine) off the assembly line that year. These last six digits will match the last six digits of VIN of the car it came from.

The engine production code is stamped on the left side of the block on the head mounting surface. The number is positioned so it is just visible on the assembled engine below and between the #1 and #3 spark plugs. Unfortuantely, this number sometimes gets destroyed if the block face is machined (decked). One source indicates some 74 engine production code numbers were placed on a sticker atop the left rocker arm cover.

The number will be in the form of XB333, where X= 1973 model, B= 350 cid-4bbl, 333= build date, 333rd day of 1972.

Once the block is id'ed that pretty much defines how to order any original parts for the engine. As you have already found, the heads have been changed to 74 units. Parts ordering really gets complicated if parts from several engines have been combined to make one. Complexity goes up more still if parts have been modified or supplied by aftermarket sources.

Hollander's manuals will tell which parts from different years or brands will fit. Also which parts will fit with some modification. Another good a source is some of our readers who have been rebuilding 350s. GM parts lists will tell which parts will be an exact match between years and other brands. Good quality aftermarket parts suppliers and their catalogs give this information as well. Good luck on your rebuild.