I have a pair of Mulfab 115lb springs that I fitted very briefly to my +4 that you can have for £35.00 + p&p (new ones are about £90 delivered).
Although Peter told me they were suitable for cars fitted with their steering bearings, I found them a bit of a bugger to fit and needed spring compressors to get them on (and off) as they are slightly longer than the originals (310mm uncompressed).
They've done no more than 60 or so miles, but have a few scratches where the spring compressors took the paint off.
Send me a PM if you're interested, or give me a bell on 0116 2695636.
You should never use spring compressor on Morgan springs I believe as there is not enough room for them to grip properly and can be very dangerous. Their are articles on how to remove and replace on various sites, basically using long bolts in the bottom brackets to gradually release the springs and the reverse to compress.
