G'day Converse ,

The 398 stamping shows a build date of 1978 so the engine looks original .

Your mower originally had a blue catcher ,I haven't seen many blue Corvette catchers around these days.

I think your Corvette is worth saving ,getting difficult to find.

Pic of the blue catcher in link.
https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/80969/victa-corvette-high-arch-4-stroke.html

Cheers
Max.