Instead of an LS swap, swap in an electric motor
GM showed a modular electric motor swap kit at SEMA just last year that can be had with a Chevy LS transmission bolt pattern to easily pair it with a variety of transmissions. If you can't wait for that, though, EV West has another way to easily add electric power to your classic.
The company announced on Facebook that it would soon start selling a Tesla crate motor kit. And the important part is that it is fitted with brackets that allow it to be bolted into anything with mounts for either a Chevy LS or Chevy small-block V8.
https://www.autoblog.com/2020/10/02/...-ls-sbc-mount/