The Eagle rods I used had some center to center issues. Don't know if the poor machine work is typical of all their stuff, but the Ohio crankshaft crank I used was spot-on in size and finish and had some super nice fillet work. My old boss (a 35 year master machinist) was really impressed with the work for the price. It was cheaper than either the Scat or Eagle. I think it was $290 a few years ago.
Put a 350 Chevy main cap next to a 340 cap and see how worried you are about the cap ever breaking.
I'd use some good ARP studs and not worry about it.
For me the main issue with a stock 40 YO block is the wall integrity of the bores with the increased piston speed and rod angularity of a stroker crank with an overbored block when I have seen stock stroke 360's with 400 HP~ split the bores more than once.
340 3.31" stroke piston speed @ 6,500rpm = 3571 ft per minute
4" stroker motor average piston speed @ 6,500 rpm = 4316 ft per minute
http://www.thedirtforum.com/pistoncalc.htm