If the oven has the same rating & the old one had a correctly rated supply, then you should be able to swop them safely from an electrical point of view. However there may be an issue with the outside of the oven getting hotter & you would need to check with the manufacturer, try their web-site.
Built under ovens used to be built different from built in, I dont know these days.
But
If i were a manufacture I would try to be selling the same oven, for both purposes.
What is the manufacture
What is the model number.
Have you cantacted manufacture
Have you looked on the web site
If its a newish oven go to a retailer & ask them.
Give us some answer to the above & lets see what we can come up with.
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