Oops, for some reason I thought that 託る was the form in the kokugos and only GG5 had 託かる.
Yes, 託かる should be visible. [io] for 託る is fine.

When the n-gram counts are this low, I think it's better to defer to the dictionaries for form priority.
The -か- okurigana in 託かる is preferred by the vast majority of the refs (daijr/s, koj, sankoku, iwakoku, meikyo, kanjipedia, gg5, prog).
I only see "託る" in smk, shinsen, and jitenon's kokugo. We usually tag forms like this as [io].

〈と／を／に〉〈託（か）／〈言／こと〉〈付／づ〉か〉っ

Google N-gram Corpus Counts
╭─ーーーーーー─┬─────┬───────╮
│ と言付かっ　 │ 265 │ 71.2% │
│ と託っ　　　 │  46 │ 12.4% │
│ と託かっ　　 │   0 │  0.0% │
│ とことづかっ │  61 │ 16.4% │
├─ーーーーーー─┼─────┼───────┤
│ を言付かっ　 │ 388 │ 23.1% │
│ を託っ　　　 │ 964 │ 57.4% │
│ を託かっ　　 │   0 │  0.0% │
│ をことづかっ │ 327 │ 19.5% │
├─ーーーーーー─┼─────┼───────┤
│ に言付かっ　 │ 164 │ 59.4% │
│ に託っ　　　 │  57 │ 20.7% │
│ に託かっ　　 │   0 │  0.0% │
│ にことづかっ │  55 │ 19.9% │
╰─ーーーーーー─┴─────┴───────╯

@@ -8 +8 @@
-<keb>託る</keb>
+<keb>託かる</keb>
@@ -11,2 +11,2 @@
-<keb>託かる</keb>
-<ke_inf>&sK;</ke_inf>
+<keb>託る</keb>
+<ke_inf>&io;</ke_inf>

gg5, prog, luminous

Oddly, 託かる is the only form in GG5.

@@ -19,0 +20,2 @@
+<gloss>to be asked to give someone (a message, parcel, etc.)</gloss>
+<gloss>to be asked to tell someone (that)</gloss>
@@ -21 +22,0 @@
-<gloss>to be asked to</gloss>

@@ -12 +12 @@
-<ke_inf>&rK;</ke_inf>
+<ke_inf>&sK;</ke_inf>

Google N-gram Corpus Counts
╭─ーーーー─┬────┬───────╮
│ 言付かる │ 65 │ 73.0% │
│ 託る　　 │ 24 │ 27.0% │
│ 託かる　 │  0 │  0.0% │
╰─ーーーー─┴────┴───────╯

probably not as many false positives as i'd have imagined

@@ -9 +8,0 @@
-<ke_inf>&rK;</ke_inf>