Well Scott I see I'm not needed here! It sounds like you have a possible magnum heads on there and not the true LA heads. The poly, as you can see, hold down with two bolts that go into the rocker assembly as well.
Here's a photo of the 340 in my Valiant, which is dimensionally identical to your 318 (or a 360 for that matter).
Stock valve covers are more rounded on the ends, and the breather and pcv valve are located in the center of the valve covers. These are el-cheapo-deluxe chrome pieces of crap that I cut up a bit to fit with my intake manifold. I changed intakes, and I can now go back to my OEM painted valve covers for that "stealth" look.
I think if I was playing with a 318, I would look for a set of the late-model pre-magnum heads, with the casting number that ended with "302". These had better ports, and slightly smaller combustion chambers so you'll gain a little compression. All the 360 heads have larger combustion chambers and larger ports, and may cost an otherwise stock 318 some ponies. A 318 toting a C-body can use all the ponies it can get!
You need to create an album first. Check This Thread for a complete walk through.
On a side note, I noticed there is an eBay auction right now for a supposed Edelbrock 318 poly 6 pack manifold. I have no idea to tell if it really is, but that could make for a very interesting and rarely seen combanation!