Dont waste your time or money on them. Run it as is. Unless you intend to start caning it up and down the motorways, I doubt you will have any problems.
I’ve ran standard not converted engines on u/l (like many others) for thousands of miles, never hurt them at all. Admittantly when I’ve rebuilt any engine i’ve had the heads converted, but only cos its in bits there and then.
Or better still just whip the head off get the exhaust valve seats replaced anyway. Doesn’t cost the earth and you never need worry about it again. Only be off the road a week tops.
