The JP Enterprises .750 Adj. Gas Block upper half has a height of 1.313". JP Enterprises does not state if it can be pinned and I recommend contacting JP Enterprises for that information.
That would depend on personal preference as well as the barrel length etc. Email us at Techsales@opticsplanet.com and let us know what rifle you have, and we can recommend a handguard that will work for your setup.