Google N-gram Corpus Counts
╭─ーーーーー─┬─────────┬───────╮
│ 恋文　　　 │ 142.916 │  N/A  │More common word
│ 痴話文　　 │      31 │100.0% │Saito, Nikk, Daijs, Daijr + Super daijr, Koj
│ 千話文　　 │       0 │  0.0% │Nikk ; add ; [sK]
│ ラブレター │ 405.833 │  N/A  │More common word
╰─ーーーーー─┴─────────┴───────╯
Saito as the only JE, Very low ngram count and all nikkoku examples are 1712 and earlier → [arch]

@@ -5,0 +6,4 @@
+</k_ele>
+<k_ele>
+<keb>千話文</keb>
+<ke_inf>&sK;</ke_inf>
@@ -11,0 +16 @@
+<misc>&arch;</misc>
@@ -12,0 +18 @@
+<gloss>billet-doux</gloss>

三省堂　スーパー大辞林; NEW斎藤和英大辞典