don't even try.........
.....to use that furnace again. too many things can go wrong , gas valves , limits , boards , motors , relays , etc..if u must diy , you have to have a pro do the startup so the temp rise , airflow , burners looking ok , draft and a complete inspection of your job for any possible safety issues. now the ac, get the correct coil & install it properly with the right clearances between the heat-x and a-coil bottom so you don't melt out the pan , and also the clearances to the top of the plenum. You see , there's a lot more to this game that meets the eye , hire a pro for assistance so there are no unpleasant surprises at startup time , good luck & regards............Jack