This just an opinion OK.
I have used the umbrella type with no problems whatsoever, the racing o-ring type keep less oil out if you are running loose clearances such as you would use for racing. The valve guide needs to be machined for them but if you have solid bronze inserts they will probably fit right on. I like the umbrella for the street as they lubricate the guide more and work just fine.
Your valve springs should have a pound rating for the height you have, if not take one down to your local engine builder and have one pressure checked at that height and also with the washer at that height. Make sure you have the height dimension with you that they would be at under full lift, check them at that height also. Now you have to decide if you need the extra spring pressure that the washer would provide. I doubt it.
I would check every valve for installed height because when the seats are ground they could be anywhere. Check for coil bind while your at it. You really should install one head to make sure everything will line up and there is no clearance problems with everything installed, check to make sure your rockers are not running off the valve stem or binding on the rocker post. Push rod lengths should be checked as well.
This is where a lot of beginner engine builders make mistakes, it really pays to mock up the engine dry to check out the valve train, especially if you have shaved the heads, decked the block etc.
To save time you can just mock one cylinder with valves installed with some light dummy springs just make sure to torque the heads down to get accurate readings. It may seem like overkill but at least you will know. The cam you have is not all that radical so I don't expect you will run into any problems.
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