Yep... the floorpans are usually cancer city but fortunately can be acquired online and not to difficult to replace if you’ve got some basic welding skills.
Prolly has the 4-bolt main block if it’s the OE engine. I’d yank it, get it bored, and run some early Vortec heads with some long tubes, mild cam (roller), etc. Beef up the tranny, go through the diffs, maybe some fatter wheels/tires and be golden.
But that’s just me.
I should try to find casting numbers and see if it is a 4 bolt or not.
A 4 bolt could rate some machining.
Besides it came out so it should go in without that much misery.