How hard/whats needed to change.....

Best for the bucks would be a 318 or the 360.

I would do the 360 and since you lready have a clutch pedal assembly you are most of the way there.

Need the trans duh you know that, ( do you have a year or model of 4 speed you want to use or have already? ) you need the bell housing and complete clutch assembly for a 360. But there is a balancing issue too and a pilot bushing goes in the crank.

You will need the shifter/rods and the T bar for the bigger clutch / bell housing. I would go with a 10 1/2 clutch should be fine. I would most likely go with a scatter sheild instead of the factory iron bell housing. But I like safety 1st.

I think that covers most of it? I know you got to cut the drive shaft too. Also you have a small 7 1/4 rear end right in a /6 car? You should also upgrade the rear end to with an 8 3/4 and depending on how the engine is and how you want it to go quick Vs fast top end gears in the 3.55 range are a good base line.