Lockhead Martin makes the C-5 Galaxy which has similar performance capabilities and in some areas exceeds the performance of the 747.
Except the design and airframe for the C-5 is not built to be a passenger aircraft. And even if such a silly "fix" were tried...even on a C-5M Super galaxy...the newest of the planes...it would still cost a LOT of money to bring it up to AF1 specs. Probably more than it would cost for two 747-8's.
There were only 131 C-5's built total. And those are spread through the Active, Reserve and Air Guard fleets. The production lines for new aircraft shut down years ago. The only way to get two C-5's for the purpose you speak of would be to pull them from the Aerospace Maintenance and Regeneration Group bone yard at Davis-Monthan AFB fly them to the Lockheed plant (after you spent the money to get them airworthy again for a special FAA one time flight certificate) and then spend $100 million per plane to bring them to the "M" specs...and that's
before any money is spent modifying them from a cargo plane into the flying White House.
There is a reason the military...in certain instances...buys "off the shelf" aircraft for conversions instead of creating a whole new genre from whole cloth.