I might cry

For a basic stock mild build they want 7g's ? Thats nuts. Not sure what they intended to do to it, but 350 hp from a 340 is like falling off a log. The stock 68-70 340's made 325 hp (not the 275 mopar claimed) from what magazine tests found.

For what you want - you dont need line honing decking or any of that stuff unless the thing is really screwed up. Just a bore job, cut the mains, resize the rods with new bolts, pistons, bearings, cam, pumps, chain gasket set, valves as needed, hard seats, and springs. Have the cam bearings installed by your shop of choice. Do a Basic valve job with new guides. Splurge a little and get it balanced as a matter of course.

I cant imagine this running more than 4 g's with you assembling it.

Find somebody else - dont even consider these outfits.