66 GMC Big Block upgrade

[Gunster89]

ok so i dont wanna sound like i dont know what im doing im 23 im still learning and i will listen to any advice that anyone has for me ive learnt I have a 66 gmc it has the 292 straight 6 in it im not sure exactly what trany I have but its a 4spd with granny and has a posy rear end I am removing my straight 6 and gettin ready to get a big block im curious what modification needs to be done to fit it in will another bell housing work or do I need a bigger tranny does anyone have any recomendations on what wiring harness to use Im not rich after a good harness but cost effective also id like pros and cons to an automatic with a shift kit in it verses a starndard shift like i have atm and recomended transmitions
basically im after a wow factor when i pop the hood thank you for the information ill post pics as I do my progress atm I am removing my engine and getting ready to paint the engine conpartment and id like to install the wire harness while the engine is out to try to hide my wires and any input on how to hide my wire would be much appreciated and any other info that you may think I could use is also welcome Ive never done an engine swap and im doing it all myself like I said all the advice you would like to ride ill take to knowledge ty again