Another Dead Engine

In the last 5 months Ive destroyed 2 motors in my Mustang. The first time was the Machinests fault, It droped a valve at about 6500 rpm because he used stock keepers.
I had the same problem on my present engine but with a set of Twisted Wedge heads
Oh well no big deal,I put my cam in a spare short block I had laying around the shop, and I borowed a set of ported and pollished stock heads from a friend and I should have her back on the road in the next few days.
Now heres my problem. Should I go back with another set of trick flow heads or something else. I wasnt realy impressed with the Trick Flows, Is there a better head on the market?

I have heard good things about World Products, but the rumor is nothing compares to airflow research.

I have World Products Windsor Sr heads on mine.They seem to work well.These ar the first and only aftermarket heads I`ve had so I can`t make any comparisons.They`ve been on the car for about 3 years or so with quite a few 6,500 rpm passes and a few 7,000 rpm runs with no problems so far.