You’ll have to dig out the stock sound deadening and mount it to the back wall. Even then, I think you’re going to have issues trying to close the seat. There is just NO clearance back there.
That being said.... I ran a kicker 8 with a 3” kenwood amp in a stock enclosure and it is what it is. It’s much louder than stock. It’s a bit muddy, partly due to the nature of amplifying a speaker level output and stock processing.
I have a stock enclosure, modified and wrapped in dynamat along with the kenwood amp and a full set of pioneer speakers for the DIY under 500 crowd that Id be willing to let go for shipping + a donation to charity.