The first indictor is the prefix of the engine number(s), also the 'front' engine mounts, the oil dip-stick tube location, and the unblocked port near the taco plate indicate Bus. The differences are actually minor and these cases
can be utilized as a building platform for a 914 motor with some easy modifications.
I don't know what the specs are on Bus cranks and rods, but I believe they are the same (1.7/1.8L). The pistons and heads make up the bigger differences with lower compression figures, so no biggie in this case (no pun intended) of these motors, since they're less than a short block anyway.
I think your pricing is in the ballpark $ range for these ... but you may want to also post them on theSAMBA classifieds - you might have a bigger audience there