I can half remember hearing stories about this back then. It would be interesting to know where the 100 acre site was, maybe that location (and/or its size, or the notion of sharing) was the deal-killer for both clubs at that time.
Yes, their higher pulling power was probably already evident by then, but the disparity has only grown severfold since, as the millions of new fans gained during the sustained success of the 70's and 80's, started to come into effect. So the differences in their stadium-needs and ours are even more stark now.
Hypothetical now of course, but not sure that 30-50k blues rattling around an 80k stadium would've been a great look. Especially if they filled it every other week and we didn't. Perhaps, if it was a practical freeby, we could've done a West Ham, stacked'em high and sold'em (very) cheap.... to get nearer filling it and winning hearts and minds that way. Don't think there's a big enough floating vote in Merseyside/North-west compared to London and the South-east for that to happen though. Interesting snippet from history though.