The AMT Model kit I'm using for this article is a '67 Chevrolet Impala SS (Picture A). I bought this at a yard sale for $3.00 (despite what the tag says.

Tools Required:

Hobby knife w/ wide blade

Hobby fine tooth saw

Epoxy for plastic repair

1/4" plastic tubing

plastic knife for mixing/applying epoxy

Parts Needed:  Interior motor cover (turnpike or reproduction)

All you'll need from your model kit is of course the body, front & rear bumpers / front & rear glass

NOTE: DO NOT use side glass if your kit comes with it as you'll need the ventilation for the motor.

1.)  Take your model body and do a test fit by putting it over your turnpike chassis to see if the wheel wells

line up with the wheels on your chassis (Picture B)

2.) Remove inner wheel wells:

Take your hobby knife and turn it so the blade is backwards (with the sharp edge facing up). Score along the top

of the inner wheel well, using the tip of the blade make an imaginary line from the firewall side to the radiator shroud 

side of the inner wheel well (Picture 1)

Continue to remove material by going over this line taking care not to press too hard so you won't slip and mar the body

(or worse take a trip to the emergency room) also score inner wheel well where it attaches to the radiator shroud (Picture 2).

As you begin to pass through the plastic with the hobby knife, turn the blade around and saw through the plastic

taking care not to travel too deep as you may saw through the outer wheel well (Picture 3)

Remove inner wheel well (Picture 4).   Repeat for other side.

3.) Clean up area left by wheel well removal by scraping with your hobby knife till it is flat (Picture 5)

(this needs to be flat for screw post mounting).

4.) Glue hood on and let dry. (Picture 6)

5.) Do a rough fit of the turnpike chassis to the body to determine the best position for the front/rear wheels

making sure your front wheels don't rub on fenders when steering.

6.) How to make screw posts with your 1/4" plastic tubing (this is available at most hobby shops) :

With chassis still sitting in car body and car upside down, lift rear of chassis till the bottom 

of chassis is even with the bottom of car body. measure the distance form the underside

of the body to the chassis screw holes (Picture 7)

Cut 2 posts to the length of what you have measured using fine tooth hobby saw. (Picture 8)

Take both posts and place them in vise jaws. Mix some Plastic repair epoxy

and place it in the holes, using a small rod to push the material down

into the holes. Finish up by covering the top of each hole with epoxy and letting it set up

for 10 minutes (or whatever amount of time your epoxy instructions say)

Once the epoxy has set up, take your chassis screw and press/screw it into

each of the screw posts, back them out and check by re-screwing them

to make sure they have set up a thread.  (Picture 9).

 

Remove screws.

Place screws into your turnpike chassis rear holes one at a time and screw the posts

on from the other side till they bottom out. (Picture 10).

place body in chassis to ensure rear screw post height. When satisfied with placement

of screw posts mark the post connecting area with red paint or marker. (Picture 11)

Now measure and repeat for the front screw posts.

7.) Once you are satisfied with the height and level of the turnpike chassis on your model

mix two part epoxy and liberally coat the end of each screw post carefully as not to get

any in the working parts of the chassis (Picture 12)

Turn chassis over and place into car body,trying not to get any epoxy on the body.

Adjust till you are satisfied with chassis alignment (Picture 13) (height,front to back placement etc..)

not forgetting the ever important front wheels ability to turn without rubbing.

LET THIS CURE OVERNIGHT.

Check alignment again by screwing chassis back into body. If all is good. Time to paint!