If you get the four-piece cork gasket, it will have two cork rails (for the long sides) and two rubber seals (for the timing chain cover bottom and the rear main cap.) If you get the one-piece moulded rubber gasket, it will go all the way around on its own. A couple useful pointers...
1) I'd get four studs, 1/4"-20 by 1" to 1.5" long (SBChevvy valve cover studs are great for this!) Install one in the third hold from each end of each rail - you'll put in four. It will save a LOT of wrestling - you get everything in place, hold the pan up with one hand (it won't move if it's on the studs,) and grab the stud nuts. Start them loosely, then you can use both hands to get the rest of the screws started.
2) Check your oil sump pan rails - lay a straightedge on them if you need to. Chances are, you managed to bugger one up breaking the seal (don't worry - we all do!) and you'll want to take a hammer and drift to straight them back out. If you don't, and it's bent, it will leak!
3) Replacement fastener sizes are 1/4"-20 x 1/2" and 5/16"-18 x 3/4". Just in case...
4) The later oil sump gasket is a little fiddly to deal with (since it's rigid,) but it's a lot easier to keep in place once it's there. Rigid long sides, you know.
USE A TORQUE WRENCH! It's painfully easy to crush that gasket - if you use the four-piece cork gasket, torque the 1/4" screws to 7 pound-feet/84 pound-inches, and the 5/16" screws to 11 pound-feet/132 pound-inches. If you use the one-piece moulded gasket, you can torque all screws to 10 pound-feet/120 pound-inches, for simplicity (that's what I did. It's close enough to manual values that I didn't feel bad using it, and my oil sump isn't leaking anymore!) Even with the later gasket (with the rigid core,) you're going for a consistent tightening of the sump rails - so you'll still want a torque wrench.
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