Bouchillon makes a kit to...
Bouchillon makes a kit to connect a 727/904 kick-down cable. The company has just developed it and is in the process of applying for a U.S. patent. Cutting-edge stuff.
Take The Plunge
Once you start down this path, there are a number of pitfalls waiting to trip you up. Most of them are clearance issues of the sort you'd expect to encounter when trying to fit two things together that were never designed for each other. To keep the number of variables down, we are assuming that if you are contemplating a new Hemi swap, you plan to keep the fuel-injection system intact. Carbureted intake manifolds are available, and some companies are making a distributor to replace the individual ignition coils, however, we don't see the logic in performing this swap and tossing the EFI stuff. If you want a carburetor, build a traditional Mopar V-8 instead.
K-Frame
The first aspect you need to decide is if you are going to keep the factory K-frame or go with an aftermarket one. The K-frame, or K-member, is a piece of stamped steel that bolts in and ties together the front of the unibody. It also serves as the engine crossmember. As you can guess, it's shaped like the letter K, and aftermarket versions are available from several companies such as XV Motorsports, RMS Chassis Components, and Magnum Force Race Car Fabrication. Everything you do to perform this swap will be based on which K-frame you're using because it's what locates the engine in the chassis. That affects what oil pan, exhaust, transmission crossmember, and accessory drive you'll need. Obviously, it is much less expensive to use the stock K-frame, but if you have access to any government bailout money, an aftermarket K offers much more clearance because it gets rid of the shock towers and torsion bars, replacing them with upper and lower control arms and coilover shocks.
TTI makes a motor mount that...
TTI makes a motor mount that will let you drop a new Hemi into any classic Mopar.
Transmission
Your next decision will be to choose a transmission. If your car is an automatic, do you want to keep your 727/904? On the new Hemi, the crank flange sticks out of the engine block a little farther than any of the previous small and big V-8s, so you'll need a special adapter and flexplate. You'll also need a starter with an extended reach to make up for the additional distance. Be sure your transmission is for a small-block, too. The big-block transmissions won't fit the new Hemi.
You'll also need to attach the 727's kick-down cable, which can be a big problem, considering the new Hemi engines all have electronic throttle bodies (see the Drive By Wire section). Bouchillon solves this problem with its newly developed kick-down cable kit that will work with the factory throttle body or an aftermarket cable-actuated throttle.
If you want an overdrive automatic, there are a couple of choices. Chrys-ler's 545RFE five-speed automatic will fit under most Mopar muscle car floorpans with a little clearancing of the floor with a hammer. You'll need to make a transmission crossmember to fit the new trans mount location, too. But the advantage of using this transmission is it can be controlled by the factory ECM. You won't need to buy a separate transmission control unit. The other option is to use a kit from Keisler that mates a GM (gasp) 4L60E with a Mopar bellhousing.
TTI was among the first to...
TTI was among the first to make swap headers that fit the new Hemi.
If you want a manual transmission, things are a little trickier. Keisler sells a kit that includes either a TKO500 or 600 and all the pedals and linkage you'll need. There will be clearance problems with this gearbox, though, and you may need to cut and reshape sections of the floor to make it fit. So far, we haven't heard of anyone adapting an old-school A833 four-speed to fit. Write us with the details if you have.
Motor Mounts
You can easily fit a new block to an older chassis with adapter plates available from several aftermarket companies. Be sure to go with the same company you will be buying your headers from. TTI sells both biscuit and spool-type mounts to cover all Mopars from '62 to '76. Street & Performance makes engine plates that adapt the new block's bolt pattern to fit 440-style frame mounts. Source your headers from S&P, too, if you go this route.
Exhaust
It cannot be stressed enough--buy the headers that match your motor mounts. TTI has this market covered and offers headers to fit the factory or an aftermarket K-frame and will clear either a 727 trans or a Keisler-supplied manual. If money or clearance is really tight, you can probably use the stock manifolds. On its website, Street & Performance details an install of a 5.7 Hemi into a '70 Challenger. S&P decided to retain the factory manifolds so the owner could keep the stock power steering system.