oil cooler snap ring and gasket?

I am rebuild my engine. The factory oil cooler was sitting in a box. A snap ring popped off the cooler. I could have swore that it came off the top of the cooler. I inspected the shaft where the oil filter attaches to and it looks like it has a grove to hold the snap ring..but I could have swore it came off the top of the cooler??? Also, the top part of the oil cooler has a perfectly flat surface that mates with the block. Is there a gasket for that part of the cooler? IF so, is it a paper gasket? OR a thick rubber piece?

HELP!!!

Not sure on the snap ring,but theres a thick flat rubber O ring gasket between the cooler and the block.

you dont realy need your oil cooler. it doesnt do that much. im assuming this is a tpi v8?? you can get your filter to screw directly into the bolck.

You could get away without an oil cooler but you would have to route your hoses and run with hotter oil.