I've also had a problem with Mark Stevens.  I ordered heads and sent cores.
The heads arrived close enough to the agreed date, but some other parts that
I thought I had ordered were not on the invoice.  A call to Norm got the
parts ordered and MS pickup up the difference to ship next day air in order
to not delay my assembly.  So for so good.  The next month there was no
credit for the $250.00 core charge put on my credit card.  Another call to
Norm informed me that the guy that went through the core heads was not taking
care of business but he would get on it.  To make a long story short 6 months
more phone calls, more excuses and no credit to my account.

After about 5000 miles one of the MS heads developed a crack between the
intake and exhaust valves.  I called Norm again to inform him of this and was
told that the 100,000 mile warranty that they have only covers dropping of
the valve seats.  I told him I was unaware of this because I never received
the warranty (something else that was never sent after numerous phone calls).
 Also mentioned that I still had not received a core credit.  He said he had
just found the paper work on a lot of heads that the former tech had
misplaced.  I told them to hold onto the money and put it towards repair of
the head I was sending back.  3 months now no money and no repaired head.

Sorry for the rambling.  I had put this all on the back burner but Bulley's
post reminded me of this situation.  I'll be calling Norm AGAIN tomorrow.

I've drawn my conclusion

John