OK If this has been answered before I missed it so please hear me out.

My barrel has the standard front sight, the kind with two pins holding it to the barrel.  I want to install a FF tube longer then the sight base.  I know I have to remove the sight and replace it with a gas block, but all I've found is blocks are ones with set screws on the bottom.  

Will this work or do I have to have a block with pins?  If I have to have pins, who makes them?

Set screw blocks are what you want for that application.

Like on these pages:

www.adcofirearms.com/sprbuild.cfm

www.eaglefirearms.net/yankee_hill.htm

Thanks, that is what I was looking for.