Stick with an HKS gasket (2.0mm thick if you want to run a lot of boost) and go with ARP bolts or studs. Studs are better in the long run, because you can reuse them, but bolts are easyer to re-install. This is because you can't remove the head from the engine in the car because it needs to come up and off of the studs. It also means that the head needs to go straight down onto the block from above, so removing the engine is needed in order to remove the head.
I would almost suggest removing the engine for a BHG anyways, just because everything is such a pain in the neck to get to when it's in the car and you can clean everything up better before reinstalling it. You don't have to, but it makes things nicer when everything is said and done.
I've got $256.50 on the 2.0mm HKS Metal Head Gasket from
http://www.andysautosport.com
I know that Andy's Auto Sport will beat any price on the stuff that they have, but they don't have everything.
I also have $113.69 on the ARP stud kit from
http://www.summitracing.com
Summit is THE cheapest outlet for new ARP fasteners.
Both places have free shipping from the warehouse outlets, just call the 1-800 numbers at the sites to make a purchase.