Dating stanley plane blades
The body and frog seem to be Type 5, but the adjuster and iron,as you said, seems to have characteristics of Type 6. The flat-top Bedrocks were all marked "Bedrock" on the bodies, and were introduced in 1911. They were often replaced in the days that a workman used his hand tools all day, every day.
I've read that some Stanley planes are a mix of types, as changes were made and old parts were used on newer planes. I think that, as you suspect, someone cut the sides down. I've worn out new plane irons in a number of planes, though not yet quite a full blade in a #8.
Almost all of Stanley's production up well into the 20th C was on the subcontractor basis (piece rate).
The main casting does not have anything other than 'No 8' cast in. The blade has 'Stanley', something illegible, and hard to say... Type 7 feature, but maybe this is also on earlier ones? My current thoughts is that it can't be a Type 5, 1885 to 1888, unless the blade was switched.
The lateral adjuster has two dates stamped in, along with 'Stanley'. The brass adjusting nut is just under 1" and is left hand threaded. Type 6 due to left hand thread and no words on the adjuster? Couple more pieces of information: Overall length is 23 11/16" Lateral adjuster is two piece version The sides have flat tops, which would imply a Bedrock version, but there is no adjuster screw to move the frog forward. Or did very early Bedrock planes not have the adjustment screw for moving the frog forward? And I will say, that I was expecting at least a 'you bought a rusty piece of crap that at one time long ago a valuable tool, but is now a door stop', or perhaps 'it's a shame that it got left outside'.
Mine wasn't much better when I bought it at a boot sale, it will take a shaving like a net curtain now, good exercise too!
Mark If you had this thread in the woodworking forum here there are a lot of experts there.