Think something like this
LCM - Mk.6 might be more practical and far more easy to make up than a LST.
At 56' in length by 14' in beam, The LCM could carry one Sherman Tank, one Half-track, one armored car or 80 troops.
The LST was a VERY large size vessel at 328' x 50' - approaching the size of the Destroyer Escorts we have with the fleet.
It actually can carry the LCM's as Deck Cargo or 4-6 regular LCVP's on divitis that can be lauched over the side not to mention Dukws, LVT's or Tanks from the well deck.