having a bit of trouble with the pony at the mo

have a sneaking suspicion the block may be frst unit

on the left hand side on the little smooth panel on the block is stamped

"LHA or LH4"

on the right hand side is stamped "ME54156"

on the back of the head ive got "81SM 6090BRA"

and "19 11 87"

inside the head wen the rocker cover is off is "171"