I have a 300 with three spd manual. Is there a 4 spd or 5 spd tranny that will mount direct to my existing bellhousing

 

4 speed, yes:

T18, NP435. Low, non-synchro first gears. Top shift, iron case, (aluminum top on NP435) heavy duty, PTO ports.

T19. A bit taller synchro first, usually behind 460s and diesels, not sure if the input shaft is compatible.

SROD, SMOD, TOD. These are 4 speed ODs based on the old Ford T&C performance "Top Loader" 4 speed. The SROD (single rail OD) and TOD (top shifted OD) are aluminum cased, considered pretty weak. The SMOD, (side-mounted shifter) is iron cased, but still has the same weak OD gear and bearing issues. 1-2-3 is similar to the 3 speed, with the 2-3 gap possibly wider. 3rd is direct, 4th is .78 or so OD.

The Top Loader itself might bolt up, not sure of your bell depth vs. the input length--2.78 first, or 2.32 for the close ratio. Good for street rod, racing etc.

5 speeds:

You can bolt a T5 (from a V8 Mustang) to an adapter and your bell. No towing or heavy loads or dropping the clutch at 7000 rpm. A tall OD so you can run those 4.56s.

The Ford issued light truck 5 speeds have integral bell housings and use hydraulic clutches.

Mazda, not a granny first, decent gear spacing, tall reverse, has some shift fork and oil leak issues in old age, but if the box is good, those can be fixed.

ZF. A HD trans, granny first, PTO ports.

Another bolt via adapter 5 speed is the NV4500 as found in Dodge and GM trucks. Some fiddling required.

More of the same:

Domestic Truck Tranny Guide

 

As the 240-300 uses the small block Ford V-8 (289, 302, 351W), use the bell housing from these for the specific trans you want to use. These tranny's all use a different bolt pattern on the face of the bellhousing. A 3 spd uses a different pattern than a T-18, and the NP 435. Another thing to consider is that the newer tranny's use an internal or external hydraulic cylinder for the clutch instead of the mechanical linkage. This would have to be fabbed.

 

Thanks guys

 

AFAIK, it depends on the year. Sometime after the mid '60s for V8s, didn't they all have the Ford "butterfly" pattern? Bell depth differs between car and truck bells in some cases also.

Pattern is visible here with an explanation:

The New Process 435 Transmission - Novak Conversions

Same pattern showing on the 4 speed OD, which also was the same on my car toploader in my Mustang, which bolted right up where the Ford 303 3 speed had been:

Toploader Imposters

Note the caution regarding bell housings here:

Toploader Imposters