Mac,
In the 1965 Shooter's Bible, page 68 there is a Model 158 that comes in 12, 16, 20 and .410 gauges. The price was $31.95 and it was called a "Topper". On page 67, there is another "Topper" without a model number that came in .30-30 or .22 Jet with a 20 gauge or .410 barrel available as an accessory for $12.00 each. Now there were "Topper Deluxe" Model 198, "Topper Jr." Model 490, "Topper Jr. Deluxe" Model 490, "Golden Squires" Model 159, "Golden Squire Jr." Model 549 and the "Mustang" Model 163, but they all had the same receiver.
In the 1983 Shooter's Bible, page 219, the "Combo Gun" was a model 058 that was in 20 Gauge with accessory barrels of .30-30 or .22 Hornet. The price was $110.00. Page 295 has another Model 058 in 12, 20 and .410 for $79.50.
Numrich offers parts for the 088 in .410 I just recently got (
H&R 088). They include .22 Jet, .22 Hornet, .30-30, .357 Mag, .44 Mag and .45-70 in addition to the shotgun parts.
It sure does look like there never was a "rifle receiver only" that H&R made for their break open single shots.
H&R made shotgun only recievers until the early 1950s and some of the early Model 48 Toppers and Model 148s were shotgun only.