MK3 head hasket.

First I was looking through either getting a 240sx with a SR20 or a mk3 supra. If anyone knows about which one is more reliable and which one costs more to modify. Well and most of all I was wondering about the supra turbo mk3 head gasket. looking at reviews it looks like that is the main problem. If i want to replace it, do I buy the stock one or what kind of a head gasket do I get? Is it from a different one, like a jdm one? If someone knows it will be helpful. thanks.