This seems a bit farfetched, but I looked though a few of the OP's historical connect walls and determined they are pretty liberal with red herrings, extra "unused matches", and stretching the idea of groups, so I am considering this at least within the realm of possibility. The key here is to note OP likes to make "at least four" words fit, that is, there can be more than four and the less likely fifth one is the one that makes it all tie together at the end.
Let's start with Rand's great start. Seems fair enough:
SWEETER THINGS - Sweet Potato, Sweet Dreams, Sweet Pea, and Sweet Soy (sweet soy sauce, for example). Why Sweeter and not Sweet? We'll get to that. Could be wrong.
I suspect this is the one Gareth and I noted:
Words that can end in 'TON'. This group arises because "Plank" has very few alternate options.
TON - Plank(ton), Single(ton), Simple(ton), Car(ton)
Now things get dicey. I found a prior connect wall with "similar homophones" and other such things, so I am going to suggest the connection is:
HT, or "words associated with things that sound like HT/TH", that is, "hit/hat/hot/th/ht". Records is actually associated with 'hit', which is how I discovered this group, but we'll need that later as you'll see.
One ('one hit wonder'), Four ('fourth'), Pink ('hot pink'), Trick ('hat trick')
Now we tread into shark infested waters. Things look grim. But wait! The connecting theme is 'things you can count on'. Well an obvious guess is
"NUMBERS", and we've already made "SWEET TON HT" (before I renamed SWEET to SWEETER). This anagrams to: ONETWTHES".
It would seem we just need "ORE" to be our last group and we've created "ONE TWO THREES", meaning "NUMBERS". Which is clued by ONE and FOUR in the grid, incidentally.
"RE" we can get by just calling Group 1 'SWEETER things' instead of 'SWEET things'. After all, they are sweeter than the other words in the wall. Which leaves "O"....
O - The 4 remaining words do indeed have the property that you can add "O" and anagram them into another English word.
Corn (Corn + O = Croon), Records (Records + O = Corrodes), Roman (Roman + O = Maroon, also more directly Romano which could be a hint), Ranch (Ranch + O = Anchor). This looks like a marvelous coincidence but it is made possible by leveraging the fact that many words fit in multiple groups, yet only one master solution puts four in each group. So it took a little finagling.
So it would seem that our four groups are found, and connected by
One, two threes, that is, the NUMBERS (7 letter solution, which truly you can count on).