Hi Im after a second hand gearbox for my 1.3 mpi felicia. First registered 19/12/97. Will the gearbox from any 1.3 skoda felicia fit mine?

It will do, but with caveats:

The mounting at the rear (down by the floor) is different on 1.3s compared to 1.6 and 1.9D, so you'd want to use your rear mounting to make sure the offset is right.

The 1.9D has a taller overall gearing - the gear ratios themselves are the same, so the rev change between gears would be the same, but it's taller, so the engine would rev less, and you'd get slower acceleration. Not sure about the gearing of a 1.6 gearbox.

The post mid-97 boxes look quite different, they're different inside as well, but functionally the same - all bolt up the same, and same clutch lever/cable and selector (once you've ground a bit off that's added to the shaft), so either will fit, without problems, AFAIK (certainly I've swapped standard boxes between cars without any problems).

there are two different end mounts to!!!!

one has a squair block inbetween two rubber pads. the other dosent

On a felicia?

one may be fav and the other felly

Yeah, I've never seen a Fel which had anything other than the rectangular mount on the chassis end. If you get a Fav box you can swap the Fel end casing for it, BUT you need an early Fel box to do that (pre-mid 97).