To start with, there is no such thing as 'Screwing On A Blower' and driving off.
This is a myth that ranks right up there with HEI ignitions, cars running on moonshine, factory differentials being 4 wheel drive and Rolls Royce offering a life time warranty.
There is much you need to do in preparation for a supercharger, even a little street charger...
The bottom end of the engine should be built as solidly as you can afford.
First thing I can think of is using a good head gasket.
Fel-Pro makes a stainless steel shim 'O' ring head gasket that will hold back boost up to about 14 psig.
After that you will have to 'O' ring heads to keep the boost pressure in.
Secondly, I'm not crazy about the unsupported cylinder walls in the 4.0 engine.
With no top deck, the cylinders may cool more evenly, but there is much less support, and Siamese cylinders are a problem all of their own!
(remember the SBC 400 and it's problems?)
Steel crank is nice, but not absolutely necessary if you stay below 7 PSIG boost.
Above 7 PSIG it's a crap shoot if your cast crank is going to live.
We have nodular iron small block Ford cranks living on 750 HP/ 735 Lb Ft. Torque engines, but don't try that with a cast SBC crank!
I've never supercharged a 4.0 Chrysler engine, but if I were you, I wouldn't experiment with MY engine...
Steel rods are a requirement as far as I'm concerned.
Cast iron and aluminum rods have problems with detonation, which a blown engine is certainly going to produce at one time or another.
A premium rod/main bearing, like Clevite 77 bearings, are a must.
Cheap bearings will delaminate and/or squish out of the contact areas.
If you can get around it, don't use a bushed rod.
(In some Fords you may not have a choice...)
the bronze bushing tends to hammer out sideways (diagonal) and allow the wrist pin/piston to cock in the bore.
Forged pistons are a MUST! You get what you pay for, and good forged pistons will be an insurance policy that is worth every cent.
Cheap cast pistons, and even the 'Hypereutectic' pistons won't live above about 5 psi boost, even if you manage to eliminate nearly all the detonation.
You need a short overlap cam shaft.
Factory cams with long over lap (so they send a good vacuum signal) won't work worth a darn and should be avoided at all costs!
Since you are making all your power down low in the RPM range, don't worry about fancy cams like roller lifter cams and such... It's a waste of time and money.
Stock type lifters, or even a lifter with some delay built in will work best.
Push rods, rockers, valve springs, ect. can all be stock below 7 PSIG boost.
More than 7 PSIG boost and you will have to step up the spring seat pressure on the intake valves to get and keep them closed.
Don't worry about high RPM anything, since a supercharger makes it's power low in the RPM range, you don't need the super high priced, super high RPM stuff...
No super expensive balancers, no roller cam with astronomical seat pressure springs, no rev kit for the roller cam, no expensive porting/polishing of the intake or head runners...
One thing you CAN do if you want to...
Clean out/up the pocket and runner of the EXHAUST valve.
With positive pressure on the intake side, this thing is going to get a breath, but to exhale can be a problem with some heads make for smog/emissions operations.
We often open up the exhaust valve, trim away the excesses in the exhaust port and runner, and put a good set of long tube headers on it.
Virtually nothing is done to the intake side except pocket clean up and port matching.
You will need a PREMIUM TRUE DOUBLE ROLLER TIMING SET.
None of the so called 'Roller' timing sets from china...
The timing chain and sprockets are going to take a beating from a supercharged engine, and you REALLY don't want the cam/ignition timing to be off!
Another thing you will need is an MSD 6 series ignition module.
Higher pressures will play hell with the stock ignition, so go ahead and get an MSD now.
Supercharged engines like a LOT of timing!
If you pipes are glowing at idle, you don't have near enough timing!
Use one of the cheap infrared temp guns on the exhaust tubes right out side the head,
(usually at the first bend is a good place)
And play with the timing.
Add some timing and the temp should go down considerably.
Lots of advance REAL QUICK.
You should be looking at 35 to 45 total advance, and all of it in by about 1,300 RPM.
Top end of the operating RPM range you want to knock back timing a little.
MSD makes a timing control module that plugs into the MSD 6 series and it will let you program some retard at higher RPM.
Questions, or shall I go on?