Buck insert install. HELP!

So I'm trying to figure out how to safely install a buck insert in my outside brick fireplace. The number of adapters and liners available is mind bogling.

Problems:
clearance above stove is only about 5 in
chimney flue is only about 5 or 6 in and the stove requires 8in liner
I can't afford to spend a ton, if I could I would just buy a new insert

I found a cast iron boot that had a pretty low profile and should solve the clearance issue.

Can 8in liner be ovalized enough to get through my flue? The price of the oval and rectangle liner is too high.

I s there no adapter that is maybe 8 in on both ends but rectangular in the middle to go through the flue. this seems like it would be a very common problem.

Thanks

Thanks for your concern. I think I was getting my terminology wrong. It's my damper that is small. the chimney itself is an all brick site built chimney designed for woodburning. So I guess the question still remains: Can I ovalize an 8 inch liner to fit through a 6in damper or do I have to buy one of these $100 adapters I've found?

I know the insert is pre EPA and not as efficient as newer models but my cost benefit anaylysis has a new setup at a minumum of $1400 (new insert and liner) vs $800 (getting this one up and running safely)

We won't be in this house forever, cannot afford a new insert and live in an area where ice storms and all electric heat are the rule. First baby on the way has me thinking of getting as prepared as possible with the resources available.