Another way you can go is using the, perhaps, more available engine from the Honda Coupe 9 circa 1968. Transverse mounted front wheel drive, 1300cc inline 4 cylinder twin cam, alloy block with 4 carbs, extractors, AIR cooled and DRY sump! 135HP, the first production engine to exceed 100HP/litre. That would be pretty good in an 800kg car and not too heavy to stick in the back of a Eureka.
Ted
Or for that matter, a Citron DS or DI. They're FMM, or front mid mount. Basically the placement or the engine/gearbox is swapped around, so the gearbox is in front of the engine. This was done so that they could retain the curvature of the long bonnet, helping to keep the drag coefficient low. Get one of the last versions, they were around 2.4 liters. Not bad for a 4 cylinder. It's just a shame that they're getting scarce, and parts are costly, especially the cv's.