"drop in" small block

Hi all, Im looking to add some more hp on dads 67 cuda. It has a nice running and sounding 273 4 bl. Just not enuf power.
So im looking at different options. I would like to do the swap over a weekend, give a day or 2.
In order to do the swap I need to borrow a buddies garage to do it in. My garage is so jammed right now there simply isnt enuf room to do a rebuilld on my 340 or to keep the cuda in over the weekend. Plus buying a running "drop in" would be quicker.
With the running 273 I obviously have all commando pieces and required brackets pulleys for 67 setup. It currently has LD4B intake and I have 4 bl carbs.
Currently it has 904 with no known issues.
Not sure how much this is gonna cost, but it would be nice to have around 300 + hp.
I have cash and lots of parts for trade. NOT lots of cash, I said parts lol.
Ideas/suggetions?
Oh car has factory 8 3/4 sg with 323
Thanks
Steve
That is a real good base, a nice 360 4 barrel would sure liven things up, I bet you can find one real cheap from your local junk yard.