Gen lll hemi install in a 67 barracuda

Welcome to the Dark Side...
There are several G3 Hemi swap threads here. I suggest you read several! The more the better.
Don't skim through, read them...
More than just a couple options for many of the changes you will need to decide on.
They all have a cascading effect downstream.
K-Member - Stock or aftermarket - stock steering or convert to rack
Torsion bars or coil over - stock steering or convert to rack
Front accessory Drive, stock G3, Car, Truck, Holley, March Performance
AC or no AC
PS or no PS, or Electric PS, or rack and pinion? Rack and Pinion does your steering choice match your K-member
Any Small block Mopar Transmission will bolt up to a G3 engine, If it's an A833, 904 or 727, no need for tunnel surgery. Kickdown for Auto will need a workaround but solutions exist. Full Manual Valve Body Automatic eliminates the need for kickdown... But if you want modern G3 performance, the 8HP70 8-speed will launch like a rocket and purrr down the freeway... 8-speed requires major tunnel surgery. Add the cost of the 8HP70 and a controller (Sound German Automotive). Will need a custom driveline too. And the shifter from a vehicle that came with an 8-speed...
Also consider rear gear ratio for modern trans vs vintage auto or manual.
Lots of cooling options, consider all the plumbing, AC, Trans cooler, Power Steering.
Radiator options, LH platform donor/new, aftermarket, original w/funky hose crossing left to right with splices... I've seen them all ;-)
Exhaust! Tight fit! Do lots of home work here and consider all the places where clearance will be impacted... Steering box, T-bars, Firewall, steering column,
Steering column to G3 Valve cover clearance... cut, mod, move...
Power Brakes? Vacuum Booster clearance? Hydro-boost?
AC- Compressor location? G3 Low mount? Mod or relocate? A Slant 6 K-Member helps with this... but there are also some other creative cost effective solutions. There are some easy more costly solutions too... Holley Accessory drive kit or March Performance. Both are pretty spendy $$$

That scratches the surface.
Every challenge has been solved before and they are pretty much all documented here in the G3 Swap forum or somewhere else.
Doing your homework up front can save you time and money by having as complete a plan as possible.

All it takes is Time, Money and Ability... It's best to have plenty of all 3! :)