6 to 8 Cyl.
I went from a \6 speed manual to a hot 360 4spd in my 68 Barracuda. Most everyone covered the items you need to change but here is how I approached it;
1. Swapped in the 4spd tranny as part of the paint and body work activities.
2. I swapped from the 9" drums to 73-76 A-body disk brakes and upgraded the torsion bars to big block bars about a year latter.
3. I swapped the 7.25 to an 8.25" suregrip rear end with 3.55 gears at the same time as the disk brakes and had the tire mounted on big bolt pattern wheels for the car.
4. I upgraded the cooling system to a v8 radiator.
All these items were done with the \6 still in the car and it was never off the road for more than a day or two. All the while I was collecting parts for the v8 swap. I rebuilt a 360, collected the clutch, bell housing parts, motor mounts and had everything ready to go for the v8 swap.
The actual swap of the 360 happened over one weekend with only a couple of odds and ends to sort out over the follwoing few days before I was back on the road.