Head work questions

Others will have their opinion, but....
1). at .030 you will have no issues. I have shaved heads .040 and never had an issue. Bolt holes actually lined up better on the intake to heads. I use Fel Pro gaskets which seal really well. Actually, if your removing the factory gaskets and going with over the counter Fel pros, you'll need to remove about .030 just to make up the difference of the gasket thickness.
2). If your intake has the holes for the dowels, then you can leave the dowels in the block.
3). I've done both ways as far as end gaskets or just RTV.
4). I would use the eddy springs. Works perfect with factory retainers, and they are 48 bucks (if I remember correctly on price). they are about the same rating as new factory 340 springs.