Everything else is going to require some real work. The issue is mostly the starter, believe it or not. Most American motors have the starter mounted below the crank center line, along the side of the oil pan. If you look at the kadett, you only have @6" from the back of the motor to back of the front crossmember, and starters are usually in the 7.5-10" length. The only way to get it to work is to make the firewall "dent" at the back of the motor wider and deeper, to allow the motor to be set back a few inches. Then, in all but the 1.9 Automatic equipped cars, which had a bigger transmission tunnel, you won't be able to get most any transmission in there. So now you're welding in a new tunnel as well. This is all really still doable, but you'll need a handy welder and there will be no going back if you wanted the car to be back to "stock."
That said, there are some motors that mount the starter in similar fashion to the Opel motor that you might be able to adapt, ie Isuzu 2.3 or Chevette 1.6, off the top of my head. Unfortunatly most of them are worse off thean a standard Opel 1.9.
If you're willing to do the firewall work, even a Ford 302 will fit between the frame rails, and the center of gravity will be moved back some so the handling should be OK. But it won't be a weekend swap, and most guys will get fustrated before they finish the priject.
Assuming the 67 kadett has a 1.1 then any engine except for a 1.1 would require surgery. Unlike a GT the kadett trans tunnel is different on a 1.1 then it is on a 1.9 or 1.5
I am speaking from expeerience when I acquired a 1.1 wagon years ago with thoughts of dropping a 1.9 in it.
front and rear ends are slightly different also
Hi , I have opportunity to buy 1968 kadett 1.2 with a dead engine , I`m not shure if I can afford to repair the engine as the spareparts are hard to get and are very expensive
I`m not familiar with the brand "opel" yet so i`m not shure where i should search for a new ,used, engine. Could you please name what model of opel should i look for. There are plenty of Kadett D and E here in Poland- would any of these fit?? or atleast maybe some parts of them are the same ?
I`m mostly interested in small engines , maybe a little bigger than the original 1.2