I just don't buy the reason for murdering Vito if Sollozzo needed Vito's connections...
Most likely because of Sonny. Because of what we fondly refer to as Sonny's 'slip', 'Sol' knew he was hot for the deal. He (and Barzini) knew that EVERYONE except Vito realized that it would be a profitable deal for all. The 'connections' would've fallen into line even with Vito Corleone dead.
Apple
A wise and frugal government, which shall leave men free to regulate their own pursuits of industry and improvement, and shall not take from the mouth of labor the bread it has earned - this is the sum of good government.
