Trans option's for my 95 monte???

Okay so here's what I have. 95' Monte Carlo Z34 with 145,000 miles on it and I think the tranny is shot. Feel's like all gear's are gone but 2nd....When in OD it doesn't take off at all....And when in drive it slip's at first and then takes off but it only get's up to about 45mph that's with hella high RPM's too. I am gonna have the car checked out to make sure that it is completely shot.... But after I find that out which I am sure I will I want to know what option's I have to replace it. I'm looking for something that will be able to handle more power than the 4T60e that is in it now, so I don't just tear it up in a few thousand miles from the hard take off's I do....And I know the later model one's have 4T65e which is supposed to handle more power. I know the 4T65e will bolt up but I don't know about any of the electrical or plug's or anything like that. And also how will this affect speed and performance? and gas millage? Also I know this would be a ton of work but I was just wondering if anyone had heard of putting a manual in one of these car's and what all that would entail? Any replies at all will be greatly appriciated....Thank's, Kevin

Make sure the gear ratio is the right one.If the gear ratio is ten teeth off,transmission will not work.On the back of the transmission,there is a metal tag with 2 big letters showing with some other numbers and letters.Those two letters will be in those small letters and numbers with a third letter and those tell what the gear ratio is(wsw,afw,etc).A motor domestic transmission repair manual will have the listing what the gear ratio is from those three letters from the metal tag.Sometimes the the electrical may need to be changed