What kind of engine can I swap out for my mitsubishi eclipse gt 2003 v6..???

There may be a few fella`s on here that know the answer to that question but may I suggest going to https://www.club3g.com/
Any ways.. welcome to the site Juan.... lots of great guys and gals on here but I don`t think you will find to much info on a 3G .This is a 1G / 2G forum...
Club 3 G will have the information you need for an engine swap. But .....Ya-all come back now ya hear

I've heard of people swapping 4G63's in and I wonder if you could drop in the DOHC 6G72TT from a 3000GT in to replace the SOHC 6G72 it came with?

From all I have read on a swap for the 6G72TT can be done but get ready to sell your house cause your going to need the capital ... There are many modifications to make just in the engine bay alone .. and the drive train...You can read up on it yourself
https://www.dsmtuners.com/threads/1999-mitsubishi-eclipse-gsx-6g72tt-swap.500411/

The 4G Eclipse 3.8L engine (6G75) can be pretty mean with full bolt-ons, like 275+ whp. It also has a 6-speed. That's a great performer if you can make it happen.