Yeh mine was the same Osvald. I took pics to ask on here but I don't think I got round to it. Just flush fitted it. I probably routed 3 or so minimal depth differences to the oak face (front face) from memory then cleaned up, the bench side I just took a gnats out with a chisel by hand.
It's been fine. I think the fixing strength is on the four bolts and the tensions exerted by the vice are shear to these and even compressive. A reasonable fit is fine I would guess. That's why I suggested giving it a go. Unless you plan on doing it up with a piece of scaff tube or tempering iron in it it for me the gamble would be whether to throw good money after bad. If you can fix it with a bolt or other means all the better. Ideal solution is welding but can be tricky/finickey I understand so maybe pricey unless you know someone or are lucky.
I got an old cast stove top welded many years ago. I was young and cabbage green and it was my only means of not dying from hypothermia in my little caravan in the wildlands of a hard Snowdonian winter. Looking back the fella moaned and groaned but he did it for pennies bless him because I was a 19 year old kid and he had a big heart and probably had kids of his own. If I walked into a local place now with the same situation I'd expect him to charge me £30 quid for the trouble at least. That's £40 quid after a broken vice. Might be different where you live.
Me. I'd fit it as is. Paid a tenner for it. If it breaks in a years time, strip it for parts, buy another, learn a lesson. The thread alone at that quality/vintage of build is a tenner in value, 2 years time you make a Moxxon vice or similar for pennies from parts you already have.
Chris