The jury at the High Court in Glasgow took only two-and-a-half hours yesterday to convict both men, who are ardent Glasgow Rangers supporters, of conspiring to assault their intended victims.
McKenzie was also found guilty of posting an item to Mr Lennon at Celtic Park with the intention of making him believe it was likely to explode or ignite and cause injury or damage to property.
The jury returned a "not proven" verdict for Muirhead on this charge. Judge Lord Turnbull said they had been convicted of "unusual but serious offences" and deferred sentence until April 27.
Speaking after the verdict, Detective Chief Superintendent John Cuddihy, the senior investigating officer, said the pair had been convicted of "the most cowardly and reckless of crimes."
"They had no thought for the very many people in the postal service and administrative offices who may have been injured or maimed by handling these packages," he added.
"Their actions certainly have nothing to do with football and everything to do with mindless hate."
The first package was sent to Mr Lennon on March 3 last year, the day after he had a touchline confrontation with Ally McCoist, then Rangers' assistant manager, following an ill-tempered cup match.
Over the next six weeks four more were sent, including another to Mr Lennon at Celtic's training ground that contained tri-acetone tri-peroxide (TATP), a volatile homemade explosive.
Two days later a third package, also containing a very small amount of TATP, was sent to Miss Godman's constituency office in Bridge of Weir, Renfrewshire.
A device containing a bottle of peroxide was sent to Cairde Na hEireann was intercepted at a postal returns depot in Belfast after it could not be delivered.
The final package was addressed to Mr McBride at Edinburgh's Advocates' Library last April. It was discovered in a postbox in Kilwinning and contained petrol, nails and a wire.
Detectives launched a major manhunt, focusing on where the contents of the devices had been bought and the packages posted.
They trawled through thousands of receipts and hours of CCTV images before pinpointing footage of McKenzie buying plastic travel bottles, padded envelopes and a watch from a local discount shop.
He was also spotted purchasing nails from a B&Q on 14 April, the day before the package for McBride was found in a postbox.
Police bugged his car and secretly recorded a man identified as him saying he had told someone how to make a bomb. Officers also heard men discussing "planting" something outside a police station.
A search of Muirhead's house uncovered petrol cans, black wire, a bottle of cream peroxide, two flags featuring the Red Hand of Ulster and a mobile phone text message referring to "our package".
Forensic experts originally told Strathclyde Police the devices were dangerous but the trial heard their electronic parts, including wires and cheap digital watches, could not act as detonators.
McKenzie admitted to police that he had constructed a "hoax bomb" posted to Mr Lennon at Celtic Park and claimed he had learned to build it from watching The A-Team, a 1980s TV show.
