With BMW Getrag 240 transmissions like the ones you’ve listed:
• “240.0.0366.91 225 3.2”
• “240.0.0366.91 225 1.4”
…both are the same basic gearbox casting/part number (240.0.0366.91) and both are 5-speed Getrag 240 manuals. The key difference is in the last number — 3.2 vs 1.4 — and that final group is widely believed among enthusiasts and tech forums to indicate a different internal specification such as gearset or final drive ratio. 
What the numbers likely mean
240.0.0366.91 – The main Getrag 240 transmission casting/part identifier. 
225 – Secondary internal code that often appears on these boxes (likely batch/variant within the 240 family). 
3.2 vs 1.4 – This suffix is not random — it refers to internal gearing or ratio variant rather than anything like model year, speedo drive presence, or number of gears. Two gearboxes with the same core casting can have different final drive ratios or internal gearing setups, affecting:
• Gear spacing / cruising revs
• Acceleration vs top-end gearing
• How the gearbox pairs with different engines or differentials
In other words:
• 3.2 would be one gearset/final drive spec
• 1.4 would be another, likely with different ratio steps
BMW/Getrag didn’t publish a simple public decoding sheet for these suffixes, so most of this knowledge comes from people physically comparing ratios and swap guides — but it does mean they are not identical inside even though the casing and main part number match. 
What that means in practice
If you’re swapping one box into a car originally fitted with the other: you can bolt it in physically, but the driving characteristics (cruising RPM, acceleration, highway gearing) may change because:
• Different final drive or gear steps change engine RPM at a given road speed
• Speedo calibration or diff compatibility might need checking
Neither suffix denotes a different number of forward gears — both are 5-speed manuals with the same basic Getrag 240 design. 
For a BMW E30 318is, the correct / original gearbox is:
Getrag 240 – code ending in 1.4
So between the two you listed, the …225 1.4 is the 318is-spec box.
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Why the 1.4 matters on a 318is
The E30 318is uses the Getrag 240 with the M42-specific gearset, which has these ratios:
Gear Ratio
1st 3.83
2nd 2.20
3rd 1.40
4th. 1.00
5th. 0.81
That 1.40 is the giveaway — the suffix is commonly understood to reference a key internal ratio (3rd gear) used to identify the gearset variant.
So:
• …1.4 → M42 / 318is gearing
• …3.2 → different internal spec (typically from another engine application)
Same casing, same bolt pattern, but not the same gearing inside.
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What happens if you use the 3.2 box instead?
It will bolt up and work, but:
• Gearing may feel shorter or oddly spaced
• Cruising RPM could change
• It won’t match the original 318is driving feel BMW intended
For originality, balance, and correct pairing with the 4.10 diff the 318is usually runs — the 1.4 box is the right one.
What the numbers likely mean
If you’re swapping one box into a car originally fitted with the other: you can bolt it in physically, but the driving characteristics (cruising RPM, acceleration, highway gearing) may change because:
Neither suffix denotes a different number of forward gears — both are 5-speed manuals with the same basic Getrag 240 design. 