Reusing head gaskets?

I've done exactly what you want to do. Keep them where the were same side and torque them 5 over what you had before. a lot of times I had to do this on motors the night before a race. Cometic steel I have used several time just keep spraying all three layers with copper coat.

This use to be an issue when heads and blocks were surface ground with a stone like a flywheel. With todays machines the surfaces are smooth depending on the machine shop used. On some when we needed a motor in a hurry we would only use one of the layers from tri-steel. This was done to raise compresion for methanal. Sometimes you have to do what has to be done. There is no grantees but its your motor and your time and money.

I've done this with always good results. A motor that was bored with a torque plate that is .030 + over bore could distort the cylinders with more than 5 over head torque so it helps to know your motor and Machine work if not a standard bore and going higher then 5. Use copper coat It is the old timers silver paint as mentioned. It doesn't help the fire ring buts prevents seepage.

I wouldn't recommend using gaskets from a fresh motor like this one from Shady Dell. The block was surfaced with a DA with the pistons installed. as were the heads. DA marks on everything even the pistons.