TopLoader to SBM 273 Bellhousing?

A Tremec TKO is available with a Ford bolt pattern. I would have to say that it robably matches the Toploader. So one option would be to obtain an aluminum BH from Silver Sport Transmissions. Or use a QuickTime BH. This could get the trans physically mounted but you still have to deal with flywheel, clutch, clutch linkage, throw out bearing, shifter, speedometer, etc.
Auto to 4 speed conversion is not cheap unless you have a donor parts car available. Even then, costs can escalate if the trans need rebuilding or clutch needs replacement. I'm currently doing a 3 soeed column shift to a 4 soeed in a 64 Val and it's been at least 2000 USD so far using factory parts. It took me about 2 yrs to collect all the bits. I imagine the costs in Switzerland are more than double. I can find a833 cores for 200-400 USD.
Using Ford oarts only complicates things and probably neans many custom parts.
If you have your heart set on a 4 speed I would recommend patience and use Chrysler parts.

Toploader 4 Speed Transmissions