Short Hub vs Long Hub - 270 & 280 Lower Unit
Typically the 302 (Ford based block) would have a 280 but not always.
Easiest way to tell the difference between a 280 and 270 lower is the exhaust outlet. The 270 has a little football helmet looking exhaust piece #4 on the attached schematic, while the 280 exhaust exits the cavitation plate.
There are two types of propellers for the 270 or the 280. The props are either long or short hub.
The long hub prop shaft is 5.375” to the end.
The prop can be either Right hand or Left Hand. Both the long and short hub props are about $315
each.
You should measure the shaft to determine whether you have the short hub (you probably do) or the long hub (most of the 270s were short hub and most of the 280s were long but not completely).
Volvo Penta drives can be run in either position so you can have forward be in the A position or forward in the B position. The outdrive doesn’t care (unlike the Mercruiser drives that do care).
But whichever way you decide to set it up the props have to match.
If you are floating in the water behind the boat and are looking at the prop rotation a right handed prop will turn clockwise (same direction as the shaft is turning).