Both are floor mounted manuals This is a 1973 Challenger rally 3 speed on the floor

Can you convert to a 4 speed pistol grip without altering the car.

Tunnel would be the same. Just the trans, drive shaft and the shifter would chang, not sure about the bell. Alot of the exterior clutch stuff maybe can be used (Fork, et al).

Bellhousing should be the same if its the dual bolt pattern one.

I would be surprised if it's not a dual bolt pattern bellhousing - that's why they made them, so that they didn't have to make separate bellhousings for 3 speeds and 4 speeds. If you take the 3 speed transmission out (leaving the bellhousing in) and there are 8 mounting holes, you're good. You then should be able to just put the 4 speed in, with a 4 speed shifter and shift rods, and have your driveshaft shortened to the right length. I believe the transmission yoke is different for the 3 speeds and 4 speeds also, so that will most likely need to be changed. You will also need to get 4 speed E body transmission levers. The shifter mounting bracket may be the same between the 3 speeds and 4 speeds, but I’m not sure. The shift rods from the 3 speed may be able to be used as the 1-2 and 3-4 rods on the 4 speed, but I’m not sure on that either. If they do, you would only have to get a reverse rod for the 4 speed. The best thing to do would be to test assemble the transmission, shifter, shifter bracket, levers and rods outside of the car first, and adjust the rods at that time – it’s much easier to adjust them outside the car than in the car. Then make sure the adjusters don’t spin when you disassemble it and install it in the car. The clutch, clutch linkage, Z bar, etc won't need to be changed, or even removed while you make the swap, but if the clutch, throwout bearing, and pilot bushing are old and getting worn out, you may want to replace them while you’ve got it apart.

You didn't mention which trans you have.Don't forget the bearing retainer size.The late 3 speed will have a larger one as opposed to an early (before 68-9?)4 spd trans.You can change that to match with the correct(same front bearing different retainer) trans.The all syncro 3 spd for a BB (stock in 70 up Roadrunner and more) has the large bolt pattern same as a 4 spd.I don't think they used the smaller A-250 trans that late with V-8, maybe in a six.

The car is a 1973 Challenger with the floor mount 3 speed Does anyone make a conversion kit

Thanx guys for all the input

The kits that I've seen advertised are for converting an automatic to a four speed. They are expensive, and contain a bunch of parts that you won't need since you already have a floor shifted manual car. But they may make a kit up for you that would only contain what you need, and would be much cheaper than an auto to manual conversion kit. Brewers would be a good place to start - www.brewersperformance.com

If there are any decent Mopar swap meets in your area, though, you could save a ton of money getting what you need there. That would require waiting until the swap meet, though, so if you're dead set on doing it now, that won't work. You might also be able to find what you need on you local Craig's List, or find a person near you selling what you need on Ebay (buying locally with Craig's list or Ebay would give you the chance to inspect it before buying). You might want check out the for sale section here on Moparts too. But if you want parts that are new, or in like-new condition, Brewers would be the place to go. Their transmissions have a 12 month warranty too, so that's another thing to consider.

I agree call brewers they will tell you what you need. I'm pretty sure the drive shaft length is the same (do you have a broadcast sheet for you car? there is a number on it for drive shaft and could be compared to a 4spd car. The slip yoke may be different. If you get a Ebody 4spd with a shifter and linkage you should be good to go. Make sure the input spline is the same most likely a 23 spline. I need a drive shaft for a 70 cuda 3spd so if you don't use yours let me know. I live in CT also.

Not sure you need to change the driveshaft. Maybe the slip yoke, but not the shaft.

You need:

Small block B/E body 4 speed transmission (small bearing retainer on front)
E-body shifter with pistol grip handle
E-body shifter mounting plate (triangular aluminum)
Square shifter boot (rectangular hole)
E-body reverse shift rod (J shaped)
4 speed shift levers on side of trasmission

You can re-use your original driveshaft, clutch, bellhousing and 2 shift rods.