Restricting coolant flow at the manifold has proven to yield higher engine coolant temps than you would see with our cooler kit. Is it enough to destroy an engine? No I don't think so. BUT, as complex as the cooling systems are on these motors, it's not something I would recommend anyone do. Now, does that mean all other kits are garbage? No it certainly does not. I just prefer ours over others as it was designed with a purpose. The form and function is hard to beat.
Here's our coolant line kit for the secondary radiator. It does away with the common vaccum plugs you see used in almost every kit listed on the market except the No Limit setup.
http://powerstrokearmy.com/forums/showthread.php?t=37032
And here is our entire delete kit. Product testing results are in the thread below. On average we've seen 5* drop in ECT over a standard h&s blocker plate. As I said, may not sound like much but as taxed as the system is, every bit counts
http://powerstrokearmy.com/forums/showthread.php?t=43011
I've got plenty of both in stock. Let me know if you have any questions, I'd be glad to help