Pat,
A little research in the Feb, 61 P&A catalog (strangely revised Nov 62) shows head gaskets for early 61 409 qty 2 where the late 61 head gaskets qty 4. I'm sure the early engine had the 586 heads and the late version had 690 heads so it seems logical to say single gasket for 360 hp version and double gaskets for 380 hp and up (or anything with 690 heads). Also strange that there is no reference at all to early version 409 586 heads and I know they were still being cast as late as Dec 61 for service. Only 690 heads are listed for 61 409 engines but a note warns not to use 690 heads on early 409 engine.
http://www.gmpartswiki.com/getbigpage?pageid=65919
A little research in the Feb, 61 P&A catalog (strangely revised Nov 62) shows head gaskets for early 61 409 qty 2 where the late 61 head gaskets qty 4. I'm sure the early engine had the 586 heads and the late version had 690 heads so it seems logical to say single gasket for 360 hp version and double gaskets for 380 hp and up (or anything with 690 heads). Also strange that there is no reference at all to early version 409 586 heads and I know they were still being cast as late as Dec 61 for service. Only 690 heads are listed for 61 409 engines but a note warns not to use 690 heads on early 409 engine.
http://www.gmpartswiki.com/getbigpage?pageid=65919