I finally started porting my 081 heads. I'm basically just smoothing things out and maybe grinding the valve boss if I can figure a way to get to it. (I'll post pics soon). Probably just a longer cutter/stone will do it.

Anyways, I was figuring on new valves, but should I go 1.94/1.6 or 1.94/1.5? Ebay ~$60 for set of 16.

Also, I was wondering if I should port them to how I want it, then bring them to the machine shop to cut for larger valves, then re-port/polish to smooth they're cuts in the bowl area.

Or get some machining done, port them, then go back for a final valve job?

I assume I need the valve guides cut down some, since all the intake valves had a small ridge on the lock groove. Lift was ~.482".

 

I would port them before taking them to the machine shop.
I would open the bowl up to just smaller than the stock
valve seat. then the new larger valve job will be just right.
You can go back again a blend any hard angle under the seat
if you want to get a primo job.
For a 350 I would go 1.94x 1.60" for a 305 I would go with

1.94x 1.50.

You could take them to the machine shop to have the valve guide boss quickly cut in the bowl before starting the porting.
I use a large cylingrical shaped stone to shorten the guide
boss in the port.
Yes you'd want to machine the guide boss/ spring pocket for high lift clearance and what ever seals you'll be using.

 

If you're sure the heads are usable (not cracked, warped, etc.), then I'd suggest porting the runners from the port sides as much as possible, then hit the machine shop.

You can save a lot of porting time by having the bowls enlarged by the machinist. When the heads are set up and indicated in under the mill quill for valve seat enlargement, it's very easy to change cutters and open the valve bowls. After that, all you'll have is a little trimming and blending of the bowls to the runners. That's also a great time to cut the rocker stud bosses and cut the guides for positive seals.

Personally, for anything with a 4" bore I'd use 2.02/1.60 valves. Of course, you're limited to 1.94/1.55 valves on a 305, and only if the valve spacing will allow it in the chambers. I'm not sure how those heads are spaced.