I went with forged Hershe rods for my turbo engine, they were $1200 however that is a lot less than an rod taking out the whole engine. Same with the Diamond pistons, worth every penny in my books.
There are options for strong rods. Eagle makes a rod that only requires minimal machine work to work with a Buick 350 however custom pistons are required. This is really not a big deal though since forged pistons will have to be custom made anyways unless you fid the old TRW. PM me if you want the details on the eagle rods.
Spend some cash having the heads ported well, and yes use the oversized valves if you want. Keep in mind some of the 75 and later heads have a larger exhaust valve stock so you can use stock late ex. valves.
I would talk to Bobb from Finishline about your cam selection, he could help get you a custom ground version like his. They made a stroker 350 that was 420 hp NA however without the added stroke they would have still been about 390 hp with low compression.
So there is no reason you could not make 300-350 hp with a stock bottom end and some head porting then have some real fun with boost