The Holiday Rambler product dates back to the early '50s. It was a popular and upscale trailer into the '90s. They were once a competitor to the Airstream and probably had similar sales figures.
As the '80s arrived RVer's interest began shifting to fifthwheels and all the cheap trailer manufacturers entered the market causing the better built trailers like HR to lose sales. HR shifted their main focus to motorhomes and built thousands of high quality mhs as trailer sales slowed. HR still built good trailers but the company was caught with several hundred completed or almost completed $200k to $400k motorhomes on their storage lot in Wakarusa, IN when the economy tanked in 2007. HR went under. I'm not certain but I don't think they survived.
A clean used HR is still a good buy in a conventional or fifthwheel trailer. I think the Alumascape was a downscale product in the HR line built with slightly lesser quality and lighter weight to compete with the cheap crap coming out of Elkhart and other locations. They are still good trailers if they were maintained.
The suspension is nothing to worry about. You can buy new leaf spring packs for probably less than $100 per spring and all the shackles and hardware for another couple hundred at worst. Any good trailer repair shop, not an RV dealer, can inspect, service, and replace it if necessary.
Appliances like air conditioner, refrigerator, furnace, and water heater are important to the price you'll pay but not really important. All RV appliances are made by one of two or three manufacturers and are generic to RVS. A/Cs, refrigerators, furnaces, water heaters, water pumps, etc. can all be purchased new in the RV industry and retrofitted. I have intentionally replaced all appliances in previous trailers I've bought used.
The issues to be concerned about are roof and roof edge seams, end cap seams, air conditioner and roof vent seals, and windows and doors. If the trailer was used a lot or stored outside in the weather, seam caulking will shrink and crack leaving open seams for rain or snow melt intrustion. If this problem is allowed to continue you'll find rot in wall framing, end cap framing, and floors. If the damage is extensive, the trailer can be junk.
Fresh water tanks and plumbing as well as waste water and sewer tanks are important because they could have been damaged by failure to properly winterize trailers and are hard (not impossible) to find for out of production older RV units.
My advice would be to check operation of all appliances and systems with the trailer hooked up to power and water, water in the fresh water tank, etc. If you aren't capable of inspecting for water intrusion damage pay an RV service department an hour or two of labor to inspect it and report findings in WRITING.
If in good shape and priced right that HR could make a very nice RV for you. I would buy it over any new Keystone, or other cheapo brand trailer.