The short answer is yes. The long answer is it depends.
If the Tech head is severely worn undersize, it might still be a little loose inside of the Merkur handle. The Tech uses English threads, the Merkur metric. If both are unworn, the fit is perfect, although I believe the metric threading is technically a little larger.
Last December I purchased an aluminum handled English Tech razor that was in new condition. I shaved with it and got a great shave. The razor is very light and I wanted to see how it shaved with a heavier handle. I also have a Murker 23C. I pulled the handle and applied it to the Tech. It worked perfectly and it started me thinking about buying one of Cooncatbobs custom heavy handles to use in permanent rotation. He does beautiful work, but I hesitate to spend $40.00 plus shipping for a five dollar razor.
I am also considering making a stainless steel handle for the Tech head. I have a milling/drilling machine that I use for my other hobbies. I can convert it to a makeshift lathe, using a 3/8 inch collet to grip the material while machining the handle contours and threading. I need to find a source for some 3/8 stainless steel roundstock. I do not have a knurling tool and do not want to go to the expense of buying one. I am thinking about using my sandblaster to heavily etch a portion of the handle to create a slip free surface. I think that this is something that can easily done to produce an efficient razor handle at a reasonable cost.
Usually with the Gillette's the ones I've seen with worn under sized threads are the Old Types and even then they'll tighten down fine.
The Merkur's seem to almost be in between the #10-32 and the Metric M5.
The Muhle head is definitely Metric and won't screw onto a newly cut #10-32 handle but will screw onto many worn vintage Gillette handles.
I've got a metric Goodfella head and a fat Tech handle won't screw all the way down but a NEW Bar handle will.