First, congratulations on getting a hemi and welcome to the group. Hemis are great engine and you should get all the help and advice you need here to build it anyway you want.
Since you're new to hemis, my first bit of advice is make sure *exactly* what you've got before you tear into it and start buying parts. I'm not saying yours isn't, but for some reason, a lot of people automatically assume that any and all early hemis are 392's. Besides the 392's - (which is 'high-deck' engine by the way and comparatively rare, as Chrysler *only* used then in passenger cars and *only* in 1957 and '1958) - there were the 'low-deck' 331 and 354 Chryslers, in car, truck, industrial and marine variations - as well as both high and low-deck Dodge and DeSoto hemis - which are also completely different from each other and from their Chrysler hemi 'sisters'. If you post the numbers - usually stamped on a pad at the front of the block- or on an industrial engine, usually on a tag riveted to the side of the block - people here will be able to tell you exactly what you've got.
About your piston question. Stock-replacement-type, 10 to 1 compression pistons should be fine for the street on normal unleaded premium gas without excessively retarding the timing. Hemis, by the way are naturally less prone to detonation for a given fuel octane, compression ratio and degrees of ignition advance. than engines with conventional 'wedge type' combustion chambers. If the motor's going to get a lot of use - and particularly, hard use, on unleaded fuel, I'd think about installing hardened valve seats and swapping the stock valves for some good aftermarket stainless-steel valves.
I can't speak for the so-called "Thumper" cams, one way or the other, but you should probably hold off on choosing a cam anyway, until you figure out exactly what kind of vehicle you're going to put your engine into. Intended use, vehicle weight, tire size & gear ratio. transmission type - ie - stick or automatic - and if an automatic. converter stall speed - are all factors that need to be considered when selecting a cam and can make or break a given combination.
About fasteners. New ARP rod bolts are definitely a good thing. Stock original main cap bolts, unless there's something obviously wrong with them, are probably fine. ARP and a several other companies make chrome-moly studs for the main caps, but they're overkill and not needed on the street - especially on a near stock 'performance rebuild. If I was going to replace any of the major fasteners, rather than new main cap bolts, I'd probably get new head bolts - or if you're really "bucks up", some aftermarket chrome-moly head studs - although again, if there's nothing noticeably wrong with them, even the original stock head bolts are probably fine for what you're doing. As you get into this project, you're going to find out that hemis, compared to a lot of other, more common engines, cost a lot more to build, so save your your money by not spending it on a unnecessary parts, so you'll have it to spend on the stuff you really do need Good luck with your hemi build and keep us informed.