As long as it fits...
The mounting bolt patterns aren't likely to match unless you go with an identical replacement...but depending on the age of the toilet, there's no guarantee that the current version the same toilet will match the old holes either. Pick any toilet that'll fit the space, fill the holes that don't match up, drill new ones...connect the plumbing...you're good to go.Unless it won't fit, the best toilet for the money is the RAritan PH II...or PHC, which is the same pump on a compact base to fit in a tighter space. Price is $200-250, but worth every penny to get a toilet that'll last at least 20 years if it's kept lubricated and rebuilt every 5-6 years--and won't choke on a little too much TP.