This is for a scenario that ive been planning for a long time, it may get finished some day, but untill that point I am just going to keep on making the units untill I've got all the ones I want.
A little info on this unit. At the begining of the 20th century artillery was only realy needed as an anti-infantry weapon, big guns fired big explosive shells to decimate enemy troops. As tanks were developed to counter the general anti infantry warfare of the time artillery had to be redesigned to fall in to two categories;
Those that fired explosive shells used to kill infantry.
Those that fired solid shells designed to punch through armoured vehicles.
There are ways to simulate this in civ III, like for instance having armoured units have high stats but low HPs and having infantry have high HPs but lower attack and defence values; The anti tank guns should have high attack values, but low rate of fire, while the Anti infantry guns should have high rate of fire but low bombard value.
The artillery in civ III seems like a half and half design, required to use both types of amunition; However the requirements of each type of gun are different. Anti-tank guns need to fire solid rounds at high velocity, while anti-infantry guns need to fire high explosive shells at a lower velocity, the ability to fire shells up and over intervening terrain or obstacles is a great advantage when laying down an artillery barrage.
This would only realy be needed for a scenario, if you want to use it in game, I would recomend a artillery upgrade with a range of 3 and no resource requirement.