The M103 24 valve was also used in similar year R129 / 300 SL. Engine blocks are basically the same between the 103 / 104 , the 103 24 V has a head all to it's self that other than a distributor and round intake ports looks the same as the 104.

The 103 and 104 both have the same amount of head bolts and the oil leak / gasket issue is overblown. Some make a big deal about the " wrong " ( green ) antifreeze but hundreds of thousands of cars used green with little trouble is changed on schedule.

I'd be less concerned about head gasket issues and more concerned about the CIS / K jet injection system on any variant of the 103. Parts are very old / worn out at this point and $$ .