engine make?

[VICKY GRAVES <ALECKS@worldnet.att.net>]

I would really appreciate some help in identifying an engine which
I received as an extra part when I purchased my spit about a year ago.
It has twin SU carbs and a 3 pipe header (both on the drivers side) 
and the word MOGOW stamped on the timing chain cover. The engine number
is on a plate attached with rivets on the right hand side of the block.
The # is 18GA-U-H 11801. I am totally lost. Please help.
Thanks
John
'74 Spitfire "Kermit"