In Latin and Greek Accidence, by John Perkins, (1875) I found the following examples of verbs that have a velar consonant only in non-present stems:
The Latin language; a historical outline of its sounds, inflections, and syntax, by Charles E. Bennett (1907) says
but perhaps there are some issues with this evidence, or opposing pieces of evidence. Bennet doesn't indicate any inscriptional evidence (e.g. use of the apex) for vowel length in this word.
###Further reading
Some links to further literature that seems relevant that I found by Googling, but that I haven't processed yet:###Works cited
Allen, W. Sidney. Vox Latina, Second Edition (First published 1965, Second edition 1978)
Bennet, Charles E. The Latin language; a historical outline of its sounds, inflections, and syntax (1907)
Perkins, John. Latin and Greek Accidence (1875)
Szemerényi, Oswald. "Latin Verbs in -uo, -uere", Oswald Szemerényi, in Italic and Romance Linguistic Studies in Honor of Ernst Pulgram (1980). This seems pretty detailed! I can only see part of it through Google Books, but it looks worth a read.
###Further reading
Some links to further literature that seems relevant that I found by Googling, but that I haven't processed yet:
"On some Slavic words in -č: k from laryngeal?", by Jens Elmegård Rasmussen (1988)
"Lachmann's Law (Part 2)", by Roman Sukač (2013)
"On Latin strāgulum and strāges: -g- and analogy", by Kanehiro Nishimura, in Words and Dictionaries: A Festschrift for Professor Stanisław Stachowski on the Occassion of his 85th Birthday (2015)