Alan, I did a little bit more research about this ultraline 4400, but not be able to find any info. From the appearance of this reg, the chassis resemble a 9400 series, if it is true, the body structure of this regulator may be the same as a a 9400, but different internal valve springs because this regulator handle much lower input pressure. If the difference is only limited to the internal valve springs, you will probably have a good chance to get a low cost VCR version 9400 regulator for pick and pull, such as this one(evil bay key word: MATHESON ULTRA-LINE REGULATOR), then replace the both pressure gauges as well as the internal valve springs assembly.
forget about my suggestion, a more close look, 4400 and 9400 regulator are not the same.
Last edited by Bettatail; 05-11-2020 at 06:50 AM.