Seat tube length is not the critical measurement. Top Tube length is. With the various frame designs with compact or standard frames then seat post is easy enough to change. But a frame that is too long or short in the top tube will rarely feel right. OK-You could change the bar stem to get the bars the right distance away from you but this could affect the handling or even feel of the bike if the frame is way out on your sizing.
Your current bike fits so measure that top tube length and go for a frame with a T.T. around that length and then look at the frame and feel the weight of it. I know we all want lightweight ones but that may not be possible but a heavy frame made out of Non butted steel with a funny name you have never heard of will not be the best choice. I would also look at rear wheel drop outs and look for the "Modern" version that fits the wheel vertically in the drop outs.
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How long was I in the army? Five foot seven.
Spike Milligan